# `reprlib` — Alternate `repr()` implementation

Código-fonte: Lib/reprlib.py

O módulo `reprlib` fornece um meio de produzir representações de objetos com limites no tamanho das strings resultantes. Isso é usado no depurador Python e pode ser útil em outros contextos também.

Este módulo fornece uma classe, uma instância e uma função.

class reprlib.Repr(*, maxlevel=6, maxtuple=6, maxlist=6, maxarray=5, maxdict=4, maxset=6, maxfrozenset=6, maxdeque=6, maxstring=30, maxlong=40, maxother=30, fillvalue='...', indent=None)

  Classe que fornece serviços de formatação úteis na implementação de funções semelhantes à embutida `repr()`; limites de tamanho para diferentes tipos de objetos são adicionados para evitar a geração de representações excessivamente longas.

  Os argumentos nomeados do construtor podem ser usados como um atalho para definir os atributos da instância de `Repr`. O que significa que a inicialização a seguir:

      aRepr = reprlib.Repr(maxlevel=3)

  É equivalente a:

      aRepr = reprlib.Repr()
      aRepr.maxlevel = 3

  See section Repr Objects for more information about `Repr` attributes.

  Alterado na versão 3.12: Allow attributes to be set via keyword arguments.

reprlib.aRepr

  This is an instance of `Repr` which is used to provide the `repr()` function described below. Changing the attributes of this object will affect the size limits used by `repr()` and the Python debugger.

reprlib.repr(obj)

  This is the `repr()` method of `aRepr`. It returns a string similar to that returned by the built-in function of the same name, but with limits on most sizes.

In addition to size-limiting tools, the module also provides a decorator for detecting recursive calls to `__repr__()` and substituting a placeholder string instead.

@reprlib.recursive_repr(fillvalue='...')

  Decorator for `__repr__()` methods to detect recursive calls within the same thread. If a recursive call is made, the fillvalue is returned, otherwise, the usual `__repr__()` call is made. For example:

      >>> from reprlib import recursive_repr
      >>> class MyList(list):
      ...     @recursive_repr()
      ...     def __repr__(self):
      ...         return '<' + '|'.join(map(repr, self)) + '>'
      ...
      >>> m = MyList('abc')
      >>> m.append(m)
      >>> m.append('x')
      >>> print(m)
      <'a'|'b'|'c'|...|'x'>

  Adicionado na versão 3.2.

## Objetos Repr

`Repr` instances provide several attributes which can be used to provide size limits for the representations of different object types, and methods which format specific object types.

Repr.fillvalue

  This string is displayed for recursive references. It defaults to `...`.

  Adicionado na versão 3.11.

Repr.maxlevel

  Depth limit on the creation of recursive representations. The default is `6`.

Repr.maxdict
Repr.maxlist
Repr.maxtuple
Repr.maxset
Repr.maxfrozenset
Repr.maxdeque
Repr.maxarray

  Limits on the number of entries represented for the named object type. The default is `4` for `maxdict`, `5` for `maxarray`, and `6` for the others.

Repr.maxlong

  Maximum number of characters in the representation for an integer. Digits are dropped from the middle. The default is `40`.

Repr.maxstring

  Limit on the number of characters in the representation of the string. Note that the “normal” representation of the string is used as the character source: if escape sequences are needed in the representation, these may be mangled when the representation is shortened. The default is `30`.

Repr.maxother

  This limit is used to control the size of object types for which no specific formatting method is available on the `Repr` object. It is applied in a similar manner as `maxstring`. The default is `20`.

Repr.indent

  If this attribute is set to `None` (the default), the output is formatted with no line breaks or indentation, like the standard `repr()`. For example:

      >>> example = [
      ...     1, 'spam', {'a': 2, 'b': 'spam eggs', 'c': {3: 4.5, 6: []}}, 'ham']
      >>> import reprlib
      >>> aRepr = reprlib.Repr()
      >>> print(aRepr.repr(example))
      [1, 'spam', {'a': 2, 'b': 'spam eggs', 'c': {3: 4.5, 6: []}}, 'ham']

  If `indent` is set to a string, each recursion level is placed on its own line, indented by that string:

      >>> aRepr.indent = '-->'
      >>> print(aRepr.repr(example))
      [
      -->1,
      -->'spam',
      -->{
      -->-->'a': 2,
      -->-->'b': 'spam eggs',
      -->-->'c': {
      -->-->-->3: 4.5,
      -->-->-->6: [],
      -->-->},
      -->},
      -->'ham',
      ]

  Setting `indent` to a positive integer value behaves as if it was set to a string with that number of spaces:

      >>> aRepr.indent = 4
      >>> print(aRepr.repr(example))
      [
          1,
          'spam',
          {
              'a': 2,
              'b': 'spam eggs',
              'c': {
                  3: 4.5,
                  6: [],
              },
          },
          'ham',
      ]

  Adicionado na versão 3.12.

Repr.repr(obj)

  The equivalent to the built-in `repr()` that uses the formatting imposed by the instance.

Repr.repr1(obj, level)

  Recursive implementation used by `repr()`. This uses the type of obj to determine which formatting method to call, passing it obj and level. The type-specific methods should call `repr1()` to perform recursive formatting, with `level - 1` for the value of level in the recursive call.

Repr.repr_TYPE(obj, level)

  Formatting methods for specific types are implemented as methods with a name based on the type name. In the method name, TYPE is replaced by `'_'.join(type(obj).__name__.split())`. Dispatch to these methods is handled by `repr1()`. Type-specific methods which need to recursively format a value should call `self.repr1(subobj, level - 1)`.

## Subclassing Repr Objects

The use of dynamic dispatching by `Repr.repr1()` allows subclasses of `Repr` to add support for additional built-in object types or to modify the handling of types already supported. This example shows how special support for file objects could be added:

    import reprlib
    import sys

    class MyRepr(reprlib.Repr):

        def repr_TextIOWrapper(self, obj, level):
            if obj.name in {'<stdin>', '<stdout>', '<stderr>'}:
                return obj.name
            return repr(obj)

    aRepr = MyRepr()
    print(aRepr.repr(sys.stdin))         # prints '<stdin>'

    <stdin>