# `!reprlib` --- Alternate `repr` implementation

<div class="module" data-synopsis="Alternate repr() implementation with size limits.">

reprlib

</div>

**Source code:** `Lib/reprlib.py`

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The `!reprlib` module provides a means for producing object representations with limits on the size of the resulting strings. This is used in the Python debugger and may be useful in other contexts as well.

This module provides a class, an instance, and a function:

<div class="Repr(*, maxlevel=6, maxtuple=6, maxlist=6, maxarray=5, maxdict=4, \ maxset=6, maxfrozenset=6, maxdeque=6, maxstring=30, maxlong=40, \ maxother=30, fillvalue=&quot;...&quot;, indent=None)">

Class which provides formatting services useful in implementing functions similar to the built-in `repr`; size limits for different object types are added to avoid the generation of representations which are excessively long.

The keyword arguments of the constructor can be used as a shortcut to set the attributes of the `Repr` instance. Which means that the following initialization:

    aRepr = reprlib.Repr(maxlevel=3)

Is equivalent to:

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

See section [Repr Objects](#repr-objects) for more information about `Repr` attributes.

<div class="versionchanged">

3.12 Allow attributes to be set via keyword arguments.

</div>

</div>

<div class="data">

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.

</div>

<div class="function">

repr(obj)

This is the `~Repr.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.

</div>

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

<div class="index">

single: ...; placeholder

</div>

<div class="decorator">

recursive_repr(fillvalue="...")

Decorator for `~object.__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:

<div class="doctest">

\>\>\> 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'\>

</div>

<div class="versionadded">

3.2

</div>

</div>

## Repr Objects

`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.

<div class="attribute">

Repr.fillvalue

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

<div class="versionadded">

3.11

</div>

</div>

<div class="attribute">

Repr.maxlevel

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

</div>

<div class="attribute">

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.

</div>

<div class="attribute">

Repr.maxlong

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

</div>

<div class="attribute">

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`.

</div>

<div class="attribute">

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`.

</div>

<div class="attribute">

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:

<div class="doctest">

indent

\>\>\> 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'\]

</div>

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

<div class="doctest">

indent

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

</div>

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

<div class="doctest">

indent

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

</div>

<div class="versionadded">

3.12

</div>

</div>

<div class="method">

Repr.repr(obj)

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

</div>

<div class="method">

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.

</div>

<div class="method" data-noindex="">

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)`.

</div>

## 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:

<div class="testcode">

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\>'

</div>

<div class="testoutput">

\<stdin\>

</div>