"ast" — Arbres Syntaxiques Abstraits
************************************

**Code source :** Lib/ast.py

======================================================================

Le module "ast" permet aux applications Python de traiter la grammaire
abstraite de l'arbre syntaxique Python. La grammaire abstraite Python
elle-même est susceptible d'être modifiée à chaque nouvelle version de
Python; ce module permet de trouver à quoi la grammaire actuelle
ressemble.

Un arbre syntaxique abstrait peut être généré en passant l'option
"ast.PyCF_ONLY_AST" à la fonction native "compile()", ou en utilisant
la fonction de facilité "parse()" fournie par le module. Le résultat
est un arbre composé d'objets dont les classes héritent toutes de
"ast.AST". Un arbre syntaxique abstrait peut être compilé en code
objet Python en utilisant la fonction native "compile()".


Grammaire abstraite
===================

La grammaire abstraite est actuellement définie comme suit :

   -- ASDL's 4 builtin types are:
   -- identifier, int, string, constant

   module Python
   {
       mod = Module(stmt* body, type_ignore* type_ignores)
           | Interactive(stmt* body)
           | Expression(expr body)
           | FunctionType(expr* argtypes, expr returns)

       stmt = FunctionDef(identifier name, arguments args,
                          stmt* body, expr* decorator_list, expr? returns,
                          string? type_comment)
             | AsyncFunctionDef(identifier name, arguments args,
                                stmt* body, expr* decorator_list, expr? returns,
                                string? type_comment)

             | ClassDef(identifier name,
                expr* bases,
                keyword* keywords,
                stmt* body,
                expr* decorator_list)
             | Return(expr? value)

             | Delete(expr* targets)
             | Assign(expr* targets, expr value, string? type_comment)
             | AugAssign(expr target, operator op, expr value)
             -- 'simple' indicates that we annotate simple name without parens
             | AnnAssign(expr target, expr annotation, expr? value, int simple)

             -- use 'orelse' because else is a keyword in target languages
             | For(expr target, expr iter, stmt* body, stmt* orelse, string? type_comment)
             | AsyncFor(expr target, expr iter, stmt* body, stmt* orelse, string? type_comment)
             | While(expr test, stmt* body, stmt* orelse)
             | If(expr test, stmt* body, stmt* orelse)
             | With(withitem* items, stmt* body, string? type_comment)
             | AsyncWith(withitem* items, stmt* body, string? type_comment)

             | Raise(expr? exc, expr? cause)
             | Try(stmt* body, excepthandler* handlers, stmt* orelse, stmt* finalbody)
             | Assert(expr test, expr? msg)

             | Import(alias* names)
             | ImportFrom(identifier? module, alias* names, int? level)

             | Global(identifier* names)
             | Nonlocal(identifier* names)
             | Expr(expr value)
             | Pass | Break | Continue

             -- col_offset is the byte offset in the utf8 string the parser uses
             attributes (int lineno, int col_offset, int? end_lineno, int? end_col_offset)

             -- BoolOp() can use left & right?
       expr = BoolOp(boolop op, expr* values)
            | NamedExpr(expr target, expr value)
            | BinOp(expr left, operator op, expr right)
            | UnaryOp(unaryop op, expr operand)
            | Lambda(arguments args, expr body)
            | IfExp(expr test, expr body, expr orelse)
            | Dict(expr* keys, expr* values)
            | Set(expr* elts)
            | ListComp(expr elt, comprehension* generators)
            | SetComp(expr elt, comprehension* generators)
            | DictComp(expr key, expr value, comprehension* generators)
            | GeneratorExp(expr elt, comprehension* generators)
            -- the grammar constrains where yield expressions can occur
            | Await(expr value)
            | Yield(expr? value)
            | YieldFrom(expr value)
            -- need sequences for compare to distinguish between
            -- x < 4 < 3 and (x < 4) < 3
            | Compare(expr left, cmpop* ops, expr* comparators)
            | Call(expr func, expr* args, keyword* keywords)
            | FormattedValue(expr value, int? conversion, expr? format_spec)
            | JoinedStr(expr* values)
            | Constant(constant value, string? kind)

            -- the following expression can appear in assignment context
            | Attribute(expr value, identifier attr, expr_context ctx)
            | Subscript(expr value, expr slice, expr_context ctx)
            | Starred(expr value, expr_context ctx)
            | Name(identifier id, expr_context ctx)
            | List(expr* elts, expr_context ctx)
            | Tuple(expr* elts, expr_context ctx)

            -- can appear only in Subscript
            | Slice(expr? lower, expr? upper, expr? step)

             -- col_offset is the byte offset in the utf8 string the parser uses
             attributes (int lineno, int col_offset, int? end_lineno, int? end_col_offset)

       expr_context = Load | Store | Del

       boolop = And | Or

       operator = Add | Sub | Mult | MatMult | Div | Mod | Pow | LShift
                    | RShift | BitOr | BitXor | BitAnd | FloorDiv

       unaryop = Invert | Not | UAdd | USub

       cmpop = Eq | NotEq | Lt | LtE | Gt | GtE | Is | IsNot | In | NotIn

       comprehension = (expr target, expr iter, expr* ifs, int is_async)

       excepthandler = ExceptHandler(expr? type, identifier? name, stmt* body)
                       attributes (int lineno, int col_offset, int? end_lineno, int? end_col_offset)

       arguments = (arg* posonlyargs, arg* args, arg? vararg, arg* kwonlyargs,
                    expr* kw_defaults, arg? kwarg, expr* defaults)

       arg = (identifier arg, expr? annotation, string? type_comment)
              attributes (int lineno, int col_offset, int? end_lineno, int? end_col_offset)

       -- keyword arguments supplied to call (NULL identifier for **kwargs)
       keyword = (identifier? arg, expr value)
                  attributes (int lineno, int col_offset, int? end_lineno, int? end_col_offset)

       -- import name with optional 'as' alias.
       alias = (identifier name, identifier? asname)

       withitem = (expr context_expr, expr? optional_vars)

       type_ignore = TypeIgnore(int lineno, string tag)
   }


Les classes nœud
================

class ast.AST

   C'est la classe de base de toute classe nœud de l'AST. Les classes
   nœud courantes sont dérivées du fichier "Parser/Python.asdl", qui
   est reproduit ci-dessous. Ils sont définis dans le module C "_ast"
   et ré-exportés dans le module "ast".

   Il y a une classe définie pour chacun des symboles présents à
   gauche dans la grammaire abstraite (par exemple, "ast.stmt" ou
   "ast.expr"). En plus de cela, il y a une classe définie pour chacun
   des constructeurs présentés à droite; ces classes héritent des
   classes situées à gauche dans l'arbre. Par exemple, la classe
   "ast.BinOp" hérite de la classe "ast.expr". Pour les règles de
   réécriture avec alternatives (comme *sums*), la partie gauche est
   abstraite : seules les instances des constructeurs spécifiques aux
   nœuds sont créés.

   _fields

      Chaque classe concrète possède un attribut "_fields" donnant les
      noms de tous les nœuds enfants.

      Chaque instance d'une classe concrète possède un attribut pour
      chaque nœud enfant, du type défini par la grammaire. Par
      exemple, les instances "ast.BinOp" possèdent un attribut "left"
      de type "ast.expr".

      Si ces attributs sont marqués comme optionnels dans la grammaire
      (en utilisant un point d'interrogation "?"), la valeur peut être
      "None". Si les attributs peuvent avoir zéro ou plus valeurs
      (marqués avec un astérisque "*"), les valeurs sont représentées
      par des listes Python. Tous les attributs possibles doivent être
      présents et avoir une valeur valide pour compiler un AST avec
      "compile()".

   lineno
   col_offset
   end_lineno
   end_col_offset

      Instances of "ast.expr" and "ast.stmt" subclasses have "lineno",
      "col_offset", "lineno", and "col_offset" attributes.  The
      "lineno" and "end_lineno" are the first and last line numbers of
      source text span (1-indexed so the first line is line 1) and the
      "col_offset" and "end_col_offset" are the corresponding UTF-8
      byte offsets of the first and last tokens that generated the
      node. The UTF-8 offset is recorded because the parser uses UTF-8
      internally.

      Note that the end positions are not required by the compiler and
      are therefore optional. The end offset is *after* the last
      symbol, for example one can get the source segment of a one-line
      expression node using "source_line[node.col_offset :
      node.end_col_offset]".

   Le constructeur d'une classe "ast.T" analyse ses arguments comme
   suit :

   * S'il y a des arguments positionnels, il doit y avoir autant de
     termes dans "T._fields"; ils sont assignés comme attributs
     portant ces noms.

   * S'il y a des arguments nommés, ils définissent les attributs de
     mêmes noms avec les valeurs données.

   Par exemple, pour créer et peupler un nœud "ast.UnaryOp", on peut
   utiliser

      node = ast.UnaryOp()
      node.op = ast.USub()
      node.operand = ast.Constant()
      node.operand.value = 5
      node.operand.lineno = 0
      node.operand.col_offset = 0
      node.lineno = 0
      node.col_offset = 0

   ou, plus compact

      node = ast.UnaryOp(ast.USub(), ast.Constant(5, lineno=0, col_offset=0),
                         lineno=0, col_offset=0)

Modifié dans la version 3.8: Class "ast.Constant" is now used for all
constants.

Modifié dans la version 3.9: Simple indices are represented by their
value, extended slices are represented as tuples.

Obsolète depuis la version 3.8: Old classes "ast.Num", "ast.Str",
"ast.Bytes", "ast.NameConstant" and "ast.Ellipsis" are still
available, but they will be removed in future Python releases.  In the
meantime, instantiating them will return an instance of a different
class.

Obsolète depuis la version 3.9: Old classes "ast.Index" and
"ast.ExtSlice" are still available, but they will be removed in future
Python releases. In the meantime, instantiating them will return an
instance of a different class.

Note:

  The descriptions of the specific node classes displayed here were
  initially adapted from the fantastic Green Tree Snakes project and
  all its contributors.


Literals
--------

class ast.Constant(value)

   A constant value. The "value" attribute of the "Constant" literal
   contains the Python object it represents. The values represented
   can be simple types such as a number, string or "None", but also
   immutable container types (tuples and frozensets) if all of their
   elements are constant.

      >>> print(ast.dump(ast.parse('123', mode='eval'), indent=4))
      Expression(
          body=Constant(value=123))

class ast.FormattedValue(value, conversion, format_spec)

   Node representing a single formatting field in an f-string. If the
   string contains a single formatting field and nothing else the node
   can be isolated otherwise it appears in "JoinedStr".

   * "value" is any expression node (such as a literal, a variable, or
     a function call).

   * "conversion" is an integer:

     * -1: no formatting

     * 115: "!s" string formatting

     * 114: "!r" repr formatting

     * 97: "!a" ascii formatting

   * "format_spec" is a "JoinedStr" node representing the formatting
     of the value, or "None" if no format was specified. Both
     "conversion" and "format_spec" can be set at the same time.

class ast.JoinedStr(values)

   An f-string, comprising a series of "FormattedValue" and "Constant"
   nodes.

      >>> print(ast.dump(ast.parse('f"sin({a}) is {sin(a):.3}"', mode='eval'), indent=4))
      Expression(
          body=JoinedStr(
              values=[
                  Constant(value='sin('),
                  FormattedValue(
                      value=Name(id='a', ctx=Load()),
                      conversion=-1),
                  Constant(value=') is '),
                  FormattedValue(
                      value=Call(
                          func=Name(id='sin', ctx=Load()),
                          args=[
                              Name(id='a', ctx=Load())],
                          keywords=[]),
                      conversion=-1,
                      format_spec=JoinedStr(
                          values=[
                              Constant(value='.3')]))]))

class ast.List(elts, ctx)
class ast.Tuple(elts, ctx)

   A list or tuple. "elts" holds a list of nodes representing the
   elements. "ctx" is "Store" if the container is an assignment target
   (i.e. "(x,y)=something"), and "Load" otherwise.

      >>> print(ast.dump(ast.parse('[1, 2, 3]', mode='eval'), indent=4))
      Expression(
          body=List(
              elts=[
                  Constant(value=1),
                  Constant(value=2),
                  Constant(value=3)],
              ctx=Load()))
      >>> print(ast.dump(ast.parse('(1, 2, 3)', mode='eval'), indent=4))
      Expression(
          body=Tuple(
              elts=[
                  Constant(value=1),
                  Constant(value=2),
                  Constant(value=3)],
              ctx=Load()))

class ast.Set(elts)

   A set. "elts" holds a list of nodes representing the set's
   elements.

      >>> print(ast.dump(ast.parse('{1, 2, 3}', mode='eval'), indent=4))
      Expression(
          body=Set(
              elts=[
                  Constant(value=1),
                  Constant(value=2),
                  Constant(value=3)]))

class ast.Dict(keys, values)

   A dictionary. "keys" and "values" hold lists of nodes representing
   the keys and the values respectively, in matching order (what would
   be returned when calling "dictionary.keys()" and
   "dictionary.values()").

   When doing dictionary unpacking using dictionary literals the
   expression to be expanded goes in the "values" list, with a "None"
   at the corresponding position in "keys".

      >>> print(ast.dump(ast.parse('{"a":1, **d}', mode='eval'), indent=4))
      Expression(
          body=Dict(
              keys=[
                  Constant(value='a'),
                  None],
              values=[
                  Constant(value=1),
                  Name(id='d', ctx=Load())]))


Variables
---------

class ast.Name(id, ctx)

   A variable name. "id" holds the name as a string, and "ctx" is one
   of the following types.

class ast.Load
class ast.Store
class ast.Del

   Variable references can be used to load the value of a variable, to
   assign a new value to it, or to delete it. Variable references are
   given a context to distinguish these cases.

      >>> print(ast.dump(ast.parse('a'), indent=4))
      Module(
          body=[
              Expr(
                  value=Name(id='a', ctx=Load()))],
          type_ignores=[])

      >>> print(ast.dump(ast.parse('a = 1'), indent=4))
      Module(
          body=[
              Assign(
                  targets=[
                      Name(id='a', ctx=Store())],
                  value=Constant(value=1))],
          type_ignores=[])

      >>> print(ast.dump(ast.parse('del a'), indent=4))
      Module(
          body=[
              Delete(
                  targets=[
                      Name(id='a', ctx=Del())])],
          type_ignores=[])

class ast.Starred(value, ctx)

   A "*var" variable reference. "value" holds the variable, typically
   a "Name" node. This type must be used when building a "Call" node
   with "*args".

      >>> print(ast.dump(ast.parse('a, *b = it'), indent=4))
      Module(
          body=[
              Assign(
                  targets=[
                      Tuple(
                          elts=[
                              Name(id='a', ctx=Store()),
                              Starred(
                                  value=Name(id='b', ctx=Store()),
                                  ctx=Store())],
                          ctx=Store())],
                  value=Name(id='it', ctx=Load()))],
          type_ignores=[])


Expressions
-----------

class ast.Expr(value)

   When an expression, such as a function call, appears as a statement
   by itself with its return value not used or stored, it is wrapped
   in this container. "value" holds one of the other nodes in this
   section, a "Constant", a "Name", a "Lambda", a "Yield" or
   "YieldFrom" node.

      >>> print(ast.dump(ast.parse('-a'), indent=4))
      Module(
          body=[
              Expr(
                  value=UnaryOp(
                      op=USub(),
                      operand=Name(id='a', ctx=Load())))],
          type_ignores=[])

class ast.UnaryOp(op, operand)

   A unary operation. "op" is the operator, and "operand" any
   expression node.

class ast.UAdd
class ast.USub
class ast.Not
class ast.Invert

   Unary operator tokens. "Not" is the "not" keyword, "Invert" is the
   "~" operator.

      >>> print(ast.dump(ast.parse('not x', mode='eval'), indent=4))
      Expression(
          body=UnaryOp(
              op=Not(),
              operand=Name(id='x', ctx=Load())))

class ast.BinOp(left, op, right)

   A binary operation (like addition or division). "op" is the
   operator, and "left" and "right" are any expression nodes.

      >>> print(ast.dump(ast.parse('x + y', mode='eval'), indent=4))
      Expression(
          body=BinOp(
              left=Name(id='x', ctx=Load()),
              op=Add(),
              right=Name(id='y', ctx=Load())))

class ast.Add
class ast.Sub
class ast.Mult
class ast.Div
class ast.FloorDiv
class ast.Mod
class ast.Pow
class ast.LShift
class ast.RShift
class ast.BitOr
class ast.BitXor
class ast.BitAnd
class ast.MatMult

   Binary operator tokens.

class ast.BoolOp(op, values)

   A boolean operation, 'or' or 'and'. "op" is "Or" or "And". "values"
   are the values involved. Consecutive operations with the same
   operator, such as "a or b or c", are collapsed into one node with
   several values.

   This doesn't include "not", which is a "UnaryOp".

      >>> print(ast.dump(ast.parse('x or y', mode='eval'), indent=4))
      Expression(
          body=BoolOp(
              op=Or(),
              values=[
                  Name(id='x', ctx=Load()),
                  Name(id='y', ctx=Load())]))

class ast.And
class ast.Or

   Boolean operator tokens.

class ast.Compare(left, ops, comparators)

   A comparison of two or more values. "left" is the first value in
   the comparison, "ops" the list of operators, and "comparators" the
   list of values after the first element in the comparison.

      >>> print(ast.dump(ast.parse('1 <= a < 10', mode='eval'), indent=4))
      Expression(
          body=Compare(
              left=Constant(value=1),
              ops=[
                  LtE(),
                  Lt()],
              comparators=[
                  Name(id='a', ctx=Load()),
                  Constant(value=10)]))

class ast.Eq
class ast.NotEq
class ast.Lt
class ast.LtE
class ast.Gt
class ast.GtE
class ast.Is
class ast.IsNot
class ast.In
class ast.NotIn

   Comparison operator tokens.

class ast.Call(func, args, keywords, starargs, kwargs)

   A function call. "func" is the function, which will often be a
   "Name" or "Attribute" object. Of the arguments:

   * "args" holds a list of the arguments passed by position.

   * "keywords" holds a list of "keyword" objects representing
     arguments passed by keyword.

   When creating a "Call" node, "args" and "keywords" are required,
   but they can be empty lists. "starargs" and "kwargs" are optional.

      >>> print(ast.dump(ast.parse('func(a, b=c, *d, **e)', mode='eval'), indent=4))
      Expression(
          body=Call(
              func=Name(id='func', ctx=Load()),
              args=[
                  Name(id='a', ctx=Load()),
                  Starred(
                      value=Name(id='d', ctx=Load()),
                      ctx=Load())],
              keywords=[
                  keyword(
                      arg='b',
                      value=Name(id='c', ctx=Load())),
                  keyword(
                      value=Name(id='e', ctx=Load()))]))

class ast.keyword(arg, value)

   A keyword argument to a function call or class definition. "arg" is
   a raw string of the parameter name, "value" is a node to pass in.

class ast.IfExp(test, body, orelse)

   An expression such as "a if b else c". Each field holds a single
   node, so in the following example, all three are "Name" nodes.

      >>> print(ast.dump(ast.parse('a if b else c', mode='eval'), indent=4))
      Expression(
          body=IfExp(
              test=Name(id='b', ctx=Load()),
              body=Name(id='a', ctx=Load()),
              orelse=Name(id='c', ctx=Load())))

class ast.Attribute(value, attr, ctx)

   Attribute access, e.g. "d.keys". "value" is a node, typically a
   "Name". "attr" is a bare string giving the name of the attribute,
   and "ctx" is "Load", "Store" or "Del" according to how the
   attribute is acted on.

      >>> print(ast.dump(ast.parse('snake.colour', mode='eval'), indent=4))
      Expression(
          body=Attribute(
              value=Name(id='snake', ctx=Load()),
              attr='colour',
              ctx=Load()))

class ast.NamedExpr(target, value)

      A named expression. This AST node is produced by the assignment
      expressions operator (also known as the walrus operator). As
      opposed to the "Assign" node in which the first argument can be
      multiple nodes, in this case both "target" and "value" must be
      single nodes.

      >>> print(ast.dump(ast.parse('(x := 4)', mode='eval'), indent=4))
      Expression(
          body=NamedExpr(
              target=Name(id='x', ctx=Store()),
              value=Constant(value=4)))


Subscripting
~~~~~~~~~~~~

class ast.Subscript(value, slice, ctx)

   A subscript, such as "l[1]". "value" is the subscripted object
   (usually sequence or mapping). "slice" is an index, slice or key.
   It can be a "Tuple" and contain a "Slice". "ctx" is "Load", "Store"
   or "Del" according to the action performed with the subscript.

      >>> print(ast.dump(ast.parse('l[1:2, 3]', mode='eval'), indent=4))
      Expression(
          body=Subscript(
              value=Name(id='l', ctx=Load()),
              slice=Tuple(
                  elts=[
                      Slice(
                          lower=Constant(value=1),
                          upper=Constant(value=2)),
                      Constant(value=3)],
                  ctx=Load()),
              ctx=Load()))

class ast.Slice(lower, upper, step)

   Regular slicing (on the form "lower:upper" or "lower:upper:step").
   Can occur only inside the *slice* field of "Subscript", either
   directly or as an element of "Tuple".

      >>> print(ast.dump(ast.parse('l[1:2]', mode='eval'), indent=4))
      Expression(
          body=Subscript(
              value=Name(id='l', ctx=Load()),
              slice=Slice(
                  lower=Constant(value=1),
                  upper=Constant(value=2)),
              ctx=Load()))


Comprehensions
~~~~~~~~~~~~~~

class ast.ListComp(elt, generators)
class ast.SetComp(elt, generators)
class ast.GeneratorExp(elt, generators)
class ast.DictComp(key, value, generators)

   List and set comprehensions, generator expressions, and dictionary
   comprehensions. "elt" (or "key" and "value") is a single node
   representing the part that will be evaluated for each item.

   "generators" is a list of "comprehension" nodes.

      >>> print(ast.dump(ast.parse('[x for x in numbers]', mode='eval'), indent=4))
      Expression(
          body=ListComp(
              elt=Name(id='x', ctx=Load()),
              generators=[
                  comprehension(
                      target=Name(id='x', ctx=Store()),
                      iter=Name(id='numbers', ctx=Load()),
                      ifs=[],
                      is_async=0)]))
      >>> print(ast.dump(ast.parse('{x: x**2 for x in numbers}', mode='eval'), indent=4))
      Expression(
          body=DictComp(
              key=Name(id='x', ctx=Load()),
              value=BinOp(
                  left=Name(id='x', ctx=Load()),
                  op=Pow(),
                  right=Constant(value=2)),
              generators=[
                  comprehension(
                      target=Name(id='x', ctx=Store()),
                      iter=Name(id='numbers', ctx=Load()),
                      ifs=[],
                      is_async=0)]))
      >>> print(ast.dump(ast.parse('{x for x in numbers}', mode='eval'), indent=4))
      Expression(
          body=SetComp(
              elt=Name(id='x', ctx=Load()),
              generators=[
                  comprehension(
                      target=Name(id='x', ctx=Store()),
                      iter=Name(id='numbers', ctx=Load()),
                      ifs=[],
                      is_async=0)]))

class ast.comprehension(target, iter, ifs, is_async)

   One "for" clause in a comprehension. "target" is the reference to
   use for each element - typically a "Name" or "Tuple" node. "iter"
   is the object to iterate over. "ifs" is a list of test expressions:
   each "for" clause can have multiple "ifs".

   "is_async" indicates a comprehension is asynchronous (using an
   "async for" instead of "for"). The value is an integer (0 or 1).

      >>> print(ast.dump(ast.parse('[ord(c) for line in file for c in line]', mode='eval'),
      ...                indent=4)) # Multiple comprehensions in one.
      Expression(
          body=ListComp(
              elt=Call(
                  func=Name(id='ord', ctx=Load()),
                  args=[
                      Name(id='c', ctx=Load())],
                  keywords=[]),
              generators=[
                  comprehension(
                      target=Name(id='line', ctx=Store()),
                      iter=Name(id='file', ctx=Load()),
                      ifs=[],
                      is_async=0),
                  comprehension(
                      target=Name(id='c', ctx=Store()),
                      iter=Name(id='line', ctx=Load()),
                      ifs=[],
                      is_async=0)]))

      >>> print(ast.dump(ast.parse('(n**2 for n in it if n>5 if n<10)', mode='eval'),
      ...                indent=4)) # generator comprehension
      Expression(
          body=GeneratorExp(
              elt=BinOp(
                  left=Name(id='n', ctx=Load()),
                  op=Pow(),
                  right=Constant(value=2)),
              generators=[
                  comprehension(
                      target=Name(id='n', ctx=Store()),
                      iter=Name(id='it', ctx=Load()),
                      ifs=[
                          Compare(
                              left=Name(id='n', ctx=Load()),
                              ops=[
                                  Gt()],
                              comparators=[
                                  Constant(value=5)]),
                          Compare(
                              left=Name(id='n', ctx=Load()),
                              ops=[
                                  Lt()],
                              comparators=[
                                  Constant(value=10)])],
                      is_async=0)]))

      >>> print(ast.dump(ast.parse('[i async for i in soc]', mode='eval'),
      ...                indent=4)) # Async comprehension
      Expression(
          body=ListComp(
              elt=Name(id='i', ctx=Load()),
              generators=[
                  comprehension(
                      target=Name(id='i', ctx=Store()),
                      iter=Name(id='soc', ctx=Load()),
                      ifs=[],
                      is_async=1)]))


Statements
----------

class ast.Assign(targets, value, type_comment)

   An assignment. "targets" is a list of nodes, and "value" is a
   single node.

   Multiple nodes in "targets" represents assigning the same value to
   each. Unpacking is represented by putting a "Tuple" or "List"
   within "targets".

   type_comment

      "type_comment" is an optional string with the type annotation as
      a comment.

      >>> print(ast.dump(ast.parse('a = b = 1'), indent=4)) # Multiple assignment
      Module(
          body=[
              Assign(
                  targets=[
                      Name(id='a', ctx=Store()),
                      Name(id='b', ctx=Store())],
                  value=Constant(value=1))],
          type_ignores=[])

      >>> print(ast.dump(ast.parse('a,b = c'), indent=4)) # Unpacking
      Module(
          body=[
              Assign(
                  targets=[
                      Tuple(
                          elts=[
                              Name(id='a', ctx=Store()),
                              Name(id='b', ctx=Store())],
                          ctx=Store())],
                  value=Name(id='c', ctx=Load()))],
          type_ignores=[])

class ast.AnnAssign(target, annotation, value, simple)

   An assignment with a type annotation. "target" is a single node and
   can be a "Name", a "Attribute" or a "Subscript". "annotation" is
   the annotation, such as a "Constant" or "Name" node. "value" is a
   single optional node. "simple" is a boolean integer set to True for
   a "Name" node in "target" that do not appear in between parenthesis
   and are hence pure names and not expressions.

      >>> print(ast.dump(ast.parse('c: int'), indent=4))
      Module(
          body=[
              AnnAssign(
                  target=Name(id='c', ctx=Store()),
                  annotation=Name(id='int', ctx=Load()),
                  simple=1)],
          type_ignores=[])

      >>> print(ast.dump(ast.parse('(a): int = 1'), indent=4)) # Annotation with parenthesis
      Module(
          body=[
              AnnAssign(
                  target=Name(id='a', ctx=Store()),
                  annotation=Name(id='int', ctx=Load()),
                  value=Constant(value=1),
                  simple=0)],
          type_ignores=[])

      >>> print(ast.dump(ast.parse('a.b: int'), indent=4)) # Attribute annotation
      Module(
          body=[
              AnnAssign(
                  target=Attribute(
                      value=Name(id='a', ctx=Load()),
                      attr='b',
                      ctx=Store()),
                  annotation=Name(id='int', ctx=Load()),
                  simple=0)],
          type_ignores=[])

      >>> print(ast.dump(ast.parse('a[1]: int'), indent=4)) # Subscript annotation
      Module(
          body=[
              AnnAssign(
                  target=Subscript(
                      value=Name(id='a', ctx=Load()),
                      slice=Constant(value=1),
                      ctx=Store()),
                  annotation=Name(id='int', ctx=Load()),
                  simple=0)],
          type_ignores=[])

class ast.AugAssign(target, op, value)

   Augmented assignment, such as "a += 1". In the following example,
   "target" is a "Name" node for "x" (with the "Store" context), "op"
   is "Add", and "value" is a "Constant" with value for 1.

   The "target" attribute connot be of class "Tuple" or "List", unlike
   the targets of "Assign".

      >>> print(ast.dump(ast.parse('x += 2'), indent=4))
      Module(
          body=[
              AugAssign(
                  target=Name(id='x', ctx=Store()),
                  op=Add(),
                  value=Constant(value=2))],
          type_ignores=[])

class ast.Raise(exc, cause)

   A "raise" statement. "exc" is the exception object to be raised,
   normally a "Call" or "Name", or "None" for a standalone "raise".
   "cause" is the optional part for "y" in "raise x from y".

      >>> print(ast.dump(ast.parse('raise x from y'), indent=4))
      Module(
          body=[
              Raise(
                  exc=Name(id='x', ctx=Load()),
                  cause=Name(id='y', ctx=Load()))],
          type_ignores=[])

class ast.Assert(test, msg)

   An assertion. "test" holds the condition, such as a "Compare" node.
   "msg" holds the failure message.

      >>> print(ast.dump(ast.parse('assert x,y'), indent=4))
      Module(
          body=[
              Assert(
                  test=Name(id='x', ctx=Load()),
                  msg=Name(id='y', ctx=Load()))],
          type_ignores=[])

class ast.Delete(targets)

   Represents a "del" statement. "targets" is a list of nodes, such as
   "Name", "Attribute" or "Subscript" nodes.

      >>> print(ast.dump(ast.parse('del x,y,z'), indent=4))
      Module(
          body=[
              Delete(
                  targets=[
                      Name(id='x', ctx=Del()),
                      Name(id='y', ctx=Del()),
                      Name(id='z', ctx=Del())])],
          type_ignores=[])

class ast.Pass

   A "pass" statement.

      >>> print(ast.dump(ast.parse('pass'), indent=4))
      Module(
          body=[
              Pass()],
          type_ignores=[])

Other statements which are only applicable inside functions or loops
are described in other sections.


Imports
~~~~~~~

class ast.Import(names)

   An import statement. "names" is a list of "alias" nodes.

      >>> print(ast.dump(ast.parse('import x,y,z'), indent=4))
      Module(
          body=[
              Import(
                  names=[
                      alias(name='x'),
                      alias(name='y'),
                      alias(name='z')])],
          type_ignores=[])

class ast.ImportFrom(module, names, level)

   Represents "from x import y". "module" is a raw string of the
   'from' name, without any leading dots, or "None" for statements
   such as "from . import foo". "level" is an integer holding the
   level of the relative import (0 means absolute import).

      >>> print(ast.dump(ast.parse('from y import x,y,z'), indent=4))
      Module(
          body=[
              ImportFrom(
                  module='y',
                  names=[
                      alias(name='x'),
                      alias(name='y'),
                      alias(name='z')],
                  level=0)],
          type_ignores=[])

class ast.alias(name, asname)

   Both parameters are raw strings of the names. "asname" can be
   "None" if the regular name is to be used.

      >>> print(ast.dump(ast.parse('from ..foo.bar import a as b, c'), indent=4))
      Module(
          body=[
              ImportFrom(
                  module='foo.bar',
                  names=[
                      alias(name='a', asname='b'),
                      alias(name='c')],
                  level=2)],
          type_ignores=[])


Control flow
------------

Note:

  Optional clauses such as "else" are stored as an empty list if
  they're not present.

class ast.If(test, body, orelse)

   An "if" statement. "test" holds a single node, such as a "Compare"
   node. "body" and "orelse" each hold a list of nodes.

   "elif" clauses don't have a special representation in the AST, but
   rather appear as extra "If" nodes within the "orelse" section of
   the previous one.

      >>> print(ast.dump(ast.parse("""
      ... if x:
      ...    ...
      ... elif y:
      ...    ...
      ... else:
      ...    ...
      ... """), indent=4))
      Module(
          body=[
              If(
                  test=Name(id='x', ctx=Load()),
                  body=[
                      Expr(
                          value=Constant(value=Ellipsis))],
                  orelse=[
                      If(
                          test=Name(id='y', ctx=Load()),
                          body=[
                              Expr(
                                  value=Constant(value=Ellipsis))],
                          orelse=[
                              Expr(
                                  value=Constant(value=Ellipsis))])])],
          type_ignores=[])

class ast.For(target, iter, body, orelse, type_comment)

   A "for" loop. "target" holds the variable(s) the loop assigns to,
   as a single "Name", "Tuple" or "List" node. "iter" holds the item
   to be looped over, again as a single node. "body" and "orelse"
   contain lists of nodes to execute. Those in "orelse" are executed
   if the loop finishes normally, rather than via a "break" statement.

   type_comment

      "type_comment" is an optional string with the type annotation as
      a comment.

      >>> print(ast.dump(ast.parse("""
      ... for x in y:
      ...     ...
      ... else:
      ...     ...
      ... """), indent=4))
      Module(
          body=[
              For(
                  target=Name(id='x', ctx=Store()),
                  iter=Name(id='y', ctx=Load()),
                  body=[
                      Expr(
                          value=Constant(value=Ellipsis))],
                  orelse=[
                      Expr(
                          value=Constant(value=Ellipsis))])],
          type_ignores=[])

class ast.While(test, body, orelse)

   A "while" loop. "test" holds the condition, such as a "Compare"
   node.

      >> print(ast.dump(ast.parse("""
      ... while x:
      ...    ...
      ... else:
      ...    ...
      ... """), indent=4))
      Module(
          body=[
              While(
                  test=Name(id='x', ctx=Load()),
                  body=[
                      Expr(
                          value=Constant(value=Ellipsis))],
                  orelse=[
                      Expr(
                          value=Constant(value=Ellipsis))])],
          type_ignores=[])

class ast.Break
class ast.Continue

   The "break" and "continue" statements.

      >>> print(ast.dump(ast.parse("""\
      ... for a in b:
      ...     if a > 5:
      ...         break
      ...     else:
      ...         continue
      ...
      ... """), indent=4))
      Module(
          body=[
              For(
                  target=Name(id='a', ctx=Store()),
                  iter=Name(id='b', ctx=Load()),
                  body=[
                      If(
                          test=Compare(
                              left=Name(id='a', ctx=Load()),
                              ops=[
                                  Gt()],
                              comparators=[
                                  Constant(value=5)]),
                          body=[
                              Break()],
                          orelse=[
                              Continue()])],
                  orelse=[])],
          type_ignores=[])

class ast.Try(body, handlers, orelse, finalbody)

   "try" blocks. All attributes are list of nodes to execute, except
   for "handlers", which is a list of "ExceptHandler" nodes.

      >>> print(ast.dump(ast.parse("""
      ... try:
      ...    ...
      ... except Exception:
      ...    ...
      ... except OtherException as e:
      ...    ...
      ... else:
      ...    ...
      ... finally:
      ...    ...
      ... """), indent=4))
      Module(
          body=[
              Try(
                  body=[
                      Expr(
                          value=Constant(value=Ellipsis))],
                  handlers=[
                      ExceptHandler(
                          type=Name(id='Exception', ctx=Load()),
                          body=[
                              Expr(
                                  value=Constant(value=Ellipsis))]),
                      ExceptHandler(
                          type=Name(id='OtherException', ctx=Load()),
                          name='e',
                          body=[
                              Expr(
                                  value=Constant(value=Ellipsis))])],
                  orelse=[
                      Expr(
                          value=Constant(value=Ellipsis))],
                  finalbody=[
                      Expr(
                          value=Constant(value=Ellipsis))])],
          type_ignores=[])

class ast.ExceptHandler(type, name, body)

   A single "except" clause. "type" is the exception type it will
   match, typically a "Name" node (or "None" for a catch-all "except:"
   clause). "name" is a raw string for the name to hold the exception,
   or "None" if the clause doesn't have "as foo". "body" is a list of
   nodes.

      >>> print(ast.dump(ast.parse("""\
      ... try:
      ...     a + 1
      ... except TypeError:
      ...     pass
      ... """), indent=4))
      Module(
          body=[
              Try(
                  body=[
                      Expr(
                          value=BinOp(
                              left=Name(id='a', ctx=Load()),
                              op=Add(),
                              right=Constant(value=1)))],
                  handlers=[
                      ExceptHandler(
                          type=Name(id='TypeError', ctx=Load()),
                          body=[
                              Pass()])],
                  orelse=[],
                  finalbody=[])],
          type_ignores=[])

class ast.With(items, body, type_comment)

   A "with" block. "items" is a list of "withitem" nodes representing
   the context managers, and "body" is the indented block inside the
   context.

   type_comment

      "type_comment" is an optional string with the type annotation as
      a comment.

class ast.withitem(context_expr, optional_vars)

   A single context manager in a "with" block. "context_expr" is the
   context manager, often a "Call" node. "optional_vars" is a "Name",
   "Tuple" or "List" for the "as foo" part, or "None" if that isn't
   used.

      >>> print(ast.dump(ast.parse("""\
      ... with a as b, c as d:
      ...    something(b, d)
      ... """), indent=4))
      Module(
          body=[
              With(
                  items=[
                      withitem(
                          context_expr=Name(id='a', ctx=Load()),
                          optional_vars=Name(id='b', ctx=Store())),
                      withitem(
                          context_expr=Name(id='c', ctx=Load()),
                          optional_vars=Name(id='d', ctx=Store()))],
                  body=[
                      Expr(
                          value=Call(
                              func=Name(id='something', ctx=Load()),
                              args=[
                                  Name(id='b', ctx=Load()),
                                  Name(id='d', ctx=Load())],
                              keywords=[]))])],
          type_ignores=[])


Function and class definitions
------------------------------

class ast.FunctionDef(name, args, body, decorator_list, returns, type_comment)

   A function definition.

   * "name" is a raw string of the function name.

   * "args" is a "arguments" node.

   * "body" is the list of nodes inside the function.

   * "decorator_list" is the list of decorators to be applied, stored
     outermost first (i.e. the first in the list will be applied
     last).

   * "returns" is the return annotation.

   type_comment

      "type_comment" is an optional string with the type annotation as
      a comment.

class ast.Lambda(args, body)

   "lambda" is a minimal function definition that can be used inside
   an expression. Unlike "FunctionDef", "body" holds a single node.

      >>> print(ast.dump(ast.parse('lambda x,y: ...'), indent=4))
      Module(
          body=[
              Expr(
                  value=Lambda(
                      args=arguments(
                          posonlyargs=[],
                          args=[
                              arg(arg='x'),
                              arg(arg='y')],
                          kwonlyargs=[],
                          kw_defaults=[],
                          defaults=[]),
                      body=Constant(value=Ellipsis)))],
          type_ignores=[])

class ast.arguments(posonlyargs, args, vararg, kwonlyargs, kw_defaults, kwarg, defaults)

   The arguments for a function.

   * "posonlyargs", "args" and "kwonlyargs" are lists of "arg" nodes.

   * "vararg" and "kwarg" are single "arg" nodes, referring to the
     "*args, **kwargs" parameters.

   * "kw_defaults" is a list of default values for keyword-only
     arguments. If one is "None", the corresponding argument is
     required.

   * "defaults" is a list of default values for arguments that can be
     passed positionally. If there are fewer defaults, they correspond
     to the last n arguments.

class ast.arg(arg, annotation, type_comment)

   A single argument in a list. "arg" is a raw string of the argument
   name, "annotation" is its annotation, such as a "Str" or "Name"
   node.

   type_comment

      "type_comment" is an optional string with the type annotation as
      a comment

      >>> print(ast.dump(ast.parse("""\
      ... @decorator1
      ... @decorator2
      ... def f(a: 'annotation', b=1, c=2, *d, e, f=3, **g) -> 'return annotation':
      ...     pass
      ... """), indent=4))
      Module(
          body=[
              FunctionDef(
                  name='f',
                  args=arguments(
                      posonlyargs=[],
                      args=[
                          arg(
                              arg='a',
                              annotation=Constant(value='annotation')),
                          arg(arg='b'),
                          arg(arg='c')],
                      vararg=arg(arg='d'),
                      kwonlyargs=[
                          arg(arg='e'),
                          arg(arg='f')],
                      kw_defaults=[
                          None,
                          Constant(value=3)],
                      kwarg=arg(arg='g'),
                      defaults=[
                          Constant(value=1),
                          Constant(value=2)]),
                  body=[
                      Pass()],
                  decorator_list=[
                      Name(id='decorator1', ctx=Load()),
                      Name(id='decorator2', ctx=Load())],
                  returns=Constant(value='return annotation'))],
          type_ignores=[])

class ast.Return(value)

   A "return" statement.

      >>> print(ast.dump(ast.parse('return 4'), indent=4))
      Module(
          body=[
              Return(
                  value=Constant(value=4))],
          type_ignores=[])

class ast.Yield(value)
class ast.YieldFrom(value)

   A "yield" or "yield from" expression. Because these are
   expressions, they must be wrapped in a "Expr" node if the value
   sent back is not used.

      >>> print(ast.dump(ast.parse('yield x'), indent=4))
      Module(
          body=[
              Expr(
                  value=Yield(
                      value=Name(id='x', ctx=Load())))],
          type_ignores=[])

      >>> print(ast.dump(ast.parse('yield from x'), indent=4))
      Module(
          body=[
              Expr(
                  value=YieldFrom(
                      value=Name(id='x', ctx=Load())))],
          type_ignores=[])

class ast.Global(names)
class ast.Nonlocal(names)

   "global" and "nonlocal" statements. "names" is a list of raw
   strings.

      >>> print(ast.dump(ast.parse('global x,y,z'), indent=4))
      Module(
          body=[
              Global(
                  names=[
                      'x',
                      'y',
                      'z'])],
          type_ignores=[])

      >>> print(ast.dump(ast.parse('nonlocal x,y,z'), indent=4))
      Module(
          body=[
              Nonlocal(
                  names=[
                      'x',
                      'y',
                      'z'])],
          type_ignores=[])

class ast.ClassDef(name, bases, keywords, starargs, kwargs, body, decorator_list)

   A class definition.

   * "name" is a raw string for the class name

   * "bases" is a list of nodes for explicitly specified base classes.

   * "keywords" is a list of "keyword" nodes, principally for
     'metaclass'. Other keywords will be passed to the metaclass, as
     per PEP-3115.

   * "starargs" and "kwargs" are each a single node, as in a function
     call. starargs will be expanded to join the list of base classes,
     and kwargs will be passed to the metaclass.

   * "body" is a list of nodes representing the code within the class
     definition.

   * "decorator_list" is a list of nodes, as in "FunctionDef".

      >>> print(ast.dump(ast.parse("""\
      ... @decorator1
      ... @decorator2
      ... class Foo(base1, base2, metaclass=meta):
      ...     pass
      ... """), indent=4))
      Module(
          body=[
              ClassDef(
                  name='Foo',
                  bases=[
                      Name(id='base1', ctx=Load()),
                      Name(id='base2', ctx=Load())],
                  keywords=[
                      keyword(
                          arg='metaclass',
                          value=Name(id='meta', ctx=Load()))],
                  body=[
                      Pass()],
                  decorator_list=[
                      Name(id='decorator1', ctx=Load()),
                      Name(id='decorator2', ctx=Load())])],
          type_ignores=[])


Async and await
---------------

class ast.AsyncFunctionDef(name, args, body, decorator_list, returns, type_comment)

   An "async def" function definition. Has the same fields as
   "FunctionDef".

class ast.Await(value)

   An "await" expression. "value" is what it waits for. Only valid in
   the body of an "AsyncFunctionDef".

   >>> print(ast.dump(ast.parse("""\
   ... async def f():
   ...     await other_func()
   ... """), indent=4))
   Module(
       body=[
           AsyncFunctionDef(
               name='f',
               args=arguments(
                   posonlyargs=[],
                   args=[],
                   kwonlyargs=[],
                   kw_defaults=[],
                   defaults=[]),
               body=[
                   Expr(
                       value=Await(
                           value=Call(
                               func=Name(id='other_func', ctx=Load()),
                               args=[],
                               keywords=[])))],
               decorator_list=[])],
       type_ignores=[])

class ast.AsyncFor(target, iter, body, orelse, type_comment)
class ast.AsyncWith(items, body, type_comment)

   "async for" loops and "async with" context managers. They have the
   same fields as "For" and "With", respectively. Only valid in the
   body of an "AsyncFunctionDef".

Note:

  When a string is parsed by "ast.parse()", operator nodes (subclasses
  of "ast.operator", "ast.unaryop", "ast.cmpop", "ast.boolop" and
  "ast.expr_context") on the returned tree will be singletons. Changes
  to one will be reflected in all other occurrences of the same value
  (e.g. "ast.Add").


Outils du module "ast"
======================

À part la classe nœud, le module "ast" définit ces fonctions et
classes utilitaires pour traverser les arbres syntaxiques abstraits :

ast.parse(source, filename='<unknown>', mode='exec', *, type_comments=False, feature_version=None)

   Analyse le code source en un nœud AST. Équivalent à
   "compile(source, filename, mode, ast.PyCF_ONLY_AST)".

   If "type_comments=True" is given, the parser is modified to check
   and return type comments as specified by **PEP 484** and **PEP
   526**. This is equivalent to adding "ast.PyCF_TYPE_COMMENTS" to the
   flags passed to "compile()".  This will report syntax errors for
   misplaced type comments.  Without this flag, type comments will be
   ignored, and the "type_comment" field on selected AST nodes will
   always be "None".  In addition, the locations of "# type: ignore"
   comments will be returned as the "type_ignores" attribute of
   "Module" (otherwise it is always an empty list).

   In addition, if "mode" is "'func_type'", the input syntax is
   modified to correspond to **PEP 484** "signature type comments",
   e.g. "(str, int) -> List[str]".

   Also, setting "feature_version" to a tuple "(major, minor)" will
   attempt to parse using that Python version's grammar. Currently
   "major" must equal to "3".  For example, setting
   "feature_version=(3, 4)" will allow the use of "async" and "await"
   as variable names.  The lowest supported version is "(3, 4)"; the
   highest is "sys.version_info[0:2]".

   Avertissement:

     Il est possible de faire planter l'interpréteur Python avec des
     chaînes suffisamment grandes ou complexes lors de la compilation
     d'un objet AST dû à la limitation de la profondeur de la pile
     d'appels.

   Modifié dans la version 3.8: Added "type_comments",
   "mode='func_type'" and "feature_version".

ast.unparse(ast_obj)

   Unparse an "ast.AST" object and generate a string with code that
   would produce an equivalent "ast.AST" object if parsed back with
   "ast.parse()".

   Avertissement:

     The produced code string will not necessarily be equal to the
     original code that generated the "ast.AST" object (without any
     compiler optimizations, such as constant tuples/frozensets).

   Avertissement:

     Trying to unparse a highly complex expression would result with
     "RecursionError".

   Nouveau dans la version 3.9.

ast.literal_eval(node_or_string)

   Évalue de manière sûre un nœud expression ou une chaîne de
   caractères contenant une expression littérale Python ou un
   conteneur. La chaîne de caractères ou le nœud fourni peut seulement
   faire partie des littéraux Python suivants : chaînes de caractères,
   bytes, nombres, *n*-uplets, listes, dictionnaires, ensembles,
   booléens, et "None".

   Cela peut être utilisé pour évaluer de manière sûre la chaîne de
   caractères contenant des valeurs Python de sources non fiable sans
   avoir besoin d'analyser les valeurs elles-mêmes. Cette fonction
   n'est pas capable d'évaluer des expressions complexes arbitraires,
   par exemple impliquant des opérateurs ou de l'indexation.

   Avertissement:

     Il est possible de faire planter l'interpréteur Python avec des
     chaînes suffisamment grandes ou complexes lors de la compilation
     d'un objet AST dû à la limitation de la profondeur de la pile
     d'appels.

   Modifié dans la version 3.2: Accepte maintenant les littéraux
   suivants *bytes* et *sets*.

   Modifié dans la version 3.9: Now supports creating empty sets with
   "'set()'".

ast.get_docstring(node, clean=True)

   Renvoie la *docstring* du *node* donné (qui doit être un nœud de
   type "FunctionDef", "AsyncFunctionDef", "ClassDef", or "Module"),
   ou "None" s'il n'a pas de *docstring*. Si *clean* est vrai, cette
   fonction nettoie l'indentation de la *docstring* avec
   "inspect.cleandoc()".

   Modifié dans la version 3.5: "AsyncFunctionDef" est maintenant
   gérée

ast.get_source_segment(source, node, *, padded=False)

   Get source code segment of the *source* that generated *node*. If
   some location information ("lineno", "end_lineno", "col_offset", or
   "end_col_offset") is missing, return "None".

   If *padded* is "True", the first line of a multi-line statement
   will be padded with spaces to match its original position.

   Nouveau dans la version 3.8.

ast.fix_missing_locations(node)

   Lorsque l'on compile un arbre avec "compile()", le compilateur
   attend les attributs "lineno" et "col_offset" pour tous les nœuds
   qui les supportent. Il est fastidieux de les remplir pour les nœuds
   générés, cette fonction utilitaire ajoute ces attributs de manière
   récursive là où ils ne sont pas déjà définis, en les définissant
   comme les valeurs du nœud parent. Elle fonctionne récursivement en
   démarrant de *node*.

ast.increment_lineno(node, n=1)

   Increment the line number and end line number of each node in the
   tree starting at *node* by *n*. This is useful to "move code" to a
   different location in a file.

ast.copy_location(new_node, old_node)

   Copy source location ("lineno", "col_offset", "end_lineno", and
   "end_col_offset") from *old_node* to *new_node* if possible, and
   return *new_node*.

ast.iter_fields(node)

   Produit un *n*-uplet de "(fieldname, value)" pour chaque champ de
   "node._fields" qui est présent dans *node*.

ast.iter_child_nodes(node)

   Produit tous les nœuds enfants directs de *node*, c'est à dire,
   tous les champs qui sont des nœuds et tous les éléments des champs
   qui sont des listes de nœuds.

ast.walk(node)

   Produit récursivement tous les nœuds enfants dans l'arbre en
   commençant par *node* (*node* lui-même est inclus), sans ordre
   spécifique. C'est utile lorsque l'on souhaite modifier les nœuds
   sur place sans prêter attention au contexte.

class ast.NodeVisitor

   Classe de base pour un visiteur de nœud, qui parcourt l'arbre
   syntaxique abstrait et appelle une fonction de visite pour chacun
   des nœuds trouvés. Cette fonction peut renvoyer une valeur qui est
   transmise par la méthode "visit()".

   Cette classe est faite pour être dérivée, en ajoutant des méthodes
   de visite à la sous-classe.

   visit(node)

      Visite un nœud. L'implémentation par défaut appelle la méthode
      "self.visit_*classname*" où *classname* représente le nom de la
      classe du nœud, ou "generic_visit()" si cette méthode n'existe
      pas.

   generic_visit(node)

      Le visiteur appelle la méthode "visit()" de tous les enfants du
      nœud.

      Notons que les nœuds enfants qui possèdent une méthode de visite
      spéciale ne seront pas visités à moins que le visiteur n'appelle
      la méthode "generic_visit()" ou ne les visite lui-même.

   N'utilisez pas "NodeVisitor" si vous souhaitez appliquer des
   changements sur les nœuds lors du parcours. Pour cela, un visiteur
   spécial existe ("NodeTransformer") qui permet les modifications.

   Obsolète depuis la version 3.8: Methods "visit_Num()",
   "visit_Str()", "visit_Bytes()", "visit_NameConstant()" and
   "visit_Ellipsis()" are deprecated now and will not be called in
   future Python versions.  Add the "visit_Constant()" method to
   handle all constant nodes.

class ast.NodeTransformer

   Une sous-classe "NodeVisitor" qui traverse l'arbre syntaxique
   abstrait et permet les modifications des nœuds.

   Le "NodeTransformer" traverse l'AST et utilise la valeur renvoyée
   par les méthodes du visiteur pour remplacer ou supprimer l'ancien
   nœud. Si la valeur renvoyée par la méthode du visiteur est "None",
   le nœud est supprimé de sa position, sinon il est remplacé par la
   valeur de retour. La valeur de retour peut être le nœud original et
   dans ce cas, il n'y a pas de remplacement.

   Voici un exemple du *transformer* qui réécrit les occurrences du
   dictionnaire ("foo") en "data['foo']" :

      class RewriteName(NodeTransformer):

          def visit_Name(self, node):
              return Subscript(
                  value=Name(id='data', ctx=Load()),
                  slice=Constant(value=node.id),
                  ctx=node.ctx
              )

   Gardez en tête que si un nœud sur lequel vous travaillez a des
   nœuds enfants, vous devez transformer également ces nœuds enfant
   vous-même ou appeler d'abord la méthode "generic_visit()" sur le
   nœud.

   Pour les nœuds qui font partie d'une collection d'instructions
   (cela s'applique à tous les nœuds instruction), le visiteur peut
   aussi renvoyer la liste des nœuds plutôt qu'un seul nœud.

   If "NodeTransformer" introduces new nodes (that weren't part of
   original tree) without giving them location information (such as
   "lineno"), "fix_missing_locations()" should be called with the new
   sub-tree to recalculate the location information:

      tree = ast.parse('foo', mode='eval')
      new_tree = fix_missing_locations(RewriteName().visit(tree))

   Utilisation typique du *transformer* :

      node = YourTransformer().visit(node)

ast.dump(node, annotate_fields=True, include_attributes=False, *, indent=None)

   Return a formatted dump of the tree in *node*.  This is mainly
   useful for debugging purposes.  If *annotate_fields* is true (by
   default), the returned string will show the names and the values
   for fields. If *annotate_fields* is false, the result string will
   be more compact by omitting unambiguous field names.  Attributes
   such as line numbers and column offsets are not dumped by default.
   If this is wanted, *include_attributes* can be set to true.

   If *indent* is a non-negative integer or string, then the tree will
   be pretty-printed with that indent level.  An indent level of 0,
   negative, or """" will only insert newlines.  "None" (the default)
   selects the single line representation. Using a positive integer
   indent indents that many spaces per level.  If *indent* is a string
   (such as ""\t""), that string is used to indent each level.

   Modifié dans la version 3.9: Added the *indent* option.


Compiler Flags
==============

The following flags may be passed to "compile()" in order to change
effects on the compilation of a program:

ast.PyCF_ALLOW_TOP_LEVEL_AWAIT

   Enables support for top-level "await", "async for", "async with"
   and async comprehensions.

   Nouveau dans la version 3.8.

ast.PyCF_ONLY_AST

   Generates and returns an abstract syntax tree instead of returning
   a compiled code object.

ast.PyCF_TYPE_COMMENTS

   Enables support for **PEP 484** and **PEP 526** style type comments
   ("# type: <type>", "# type: ignore <stuff>").

   Nouveau dans la version 3.8.


Command-Line Usage
==================

Nouveau dans la version 3.9.

The "ast" module can be executed as a script from the command line. It
is as simple as:

   python -m ast [-m <mode>] [-a] [infile]

The following options are accepted:

-h, --help

   Show the help message and exit.

-m <mode>
--mode <mode>

   Specify what kind of code must be compiled, like the *mode*
   argument in "parse()".

--no-type-comments

   Don't parse type comments.

-a, --include-attributes

   Include attributes such as line numbers and column offsets.

-i <indent>
--indent <indent>

   Indentation of nodes in AST (number of spaces).

If "infile" is specified its contents are parsed to AST and dumped to
stdout.  Otherwise, the content is read from stdin.

Voir aussi:

  Green Tree Snakes, une ressource documentaire externe, qui possède
  plus de détails pour travailler avec des ASTs Python.

  ASTTokens annotates Python ASTs with the positions of tokens and
  text in the source code that generated them. This is helpful for
  tools that make source code transformations.

  leoAst.py unifies the token-based and parse-tree-based views of
  python programs by inserting two-way links between tokens and ast
  nodes.

  LibCST parses code as a Concrete Syntax Tree that looks like an ast
  tree and keeps all formatting details. It's useful for building
  automated refactoring (codemod) applications and linters.

  Parso is a Python parser that supports error recovery and round-trip
  parsing for different Python versions (in multiple Python versions).
  Parso is also able to list multiple syntax errors in your python
  file.
