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.

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_classnameclassname 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.