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"""This module defines the :class:`NiceRepr` mixin class, which defines a
``__repr__`` and ``__str__`` method that only depend on a custom ``__nice__``
method, which you must define. This means you only have to overload one
function instead of two. Furthermore, if the object defines a ``__len__``
method, then the ``__nice__`` method defaults to something sensible, otherwise
it is treated as abstract and raises ``NotImplementedError``.
To use simply have your object inherit from :class:`NiceRepr`
(multi-inheritance should be ok).
This code was copied from the ubelt library: https://github.com/Erotemic/ubelt
Example:
>>> # Objects that define __nice__ have a default __str__ and __repr__
>>> class Student(NiceRepr):
... def __init__(self, name):
... self.name = name
... def __nice__(self):
... return self.name
>>> s1 = Student('Alice')
>>> s2 = Student('Bob')
>>> print(f's1 = {s1}')
>>> print(f's2 = {s2}')
s1 = <Student(Alice)>
s2 = <Student(Bob)>
Example:
>>> # Objects that define __len__ have a default __nice__
>>> class Group(NiceRepr):
... def __init__(self, data):
... self.data = data
... def __len__(self):
... return len(self.data)
>>> g = Group([1, 2, 3])
>>> print(f'g = {g}')
g = <Group(3)>
"""
import warnings
class NiceRepr(object):
"""Inherit from this class and define ``__nice__`` to "nicely" print your
objects.
Defines ``__str__`` and ``__repr__`` in terms of ``__nice__`` function
Classes that inherit from :class:`NiceRepr` should redefine ``__nice__``.
If the inheriting class has a ``__len__``, method then the default
``__nice__`` method will return its length.
Example:
>>> class Foo(NiceRepr):
... def __nice__(self):
... return 'info'
>>> foo = Foo()
>>> assert str(foo) == '<Foo(info)>'
>>> assert repr(foo).startswith('<Foo(info) at ')
Example:
>>> class Bar(NiceRepr):
... pass
>>> bar = Bar()
>>> import pytest
>>> with pytest.warns(None) as record:
>>> assert 'object at' in str(bar)
>>> assert 'object at' in repr(bar)
Example:
>>> class Baz(NiceRepr):
... def __len__(self):
... return 5
>>> baz = Baz()
>>> assert str(baz) == '<Baz(5)>'
"""
def __nice__(self):
"""str: a "nice" summary string describing this module"""
if hasattr(self, '__len__'):
# It is a common pattern for objects to use __len__ in __nice__
# As a convenience we define a default __nice__ for these objects
return str(len(self))
else:
# In all other cases force the subclass to overload __nice__
raise NotImplementedError(
f'Define the __nice__ method for {self.__class__!r}')
def __repr__(self):
"""str: the string of the module"""
try:
nice = self.__nice__()
classname = self.__class__.__name__
return f'<{classname}({nice}) at {hex(id(self))}>'
except NotImplementedError as ex:
warnings.warn(str(ex), category=RuntimeWarning)
return object.__repr__(self)
def __str__(self):
"""str: the string of the module"""
try:
classname = self.__class__.__name__
nice = self.__nice__()
return f'<{classname}({nice})>'
except NotImplementedError as ex:
warnings.warn(str(ex), category=RuntimeWarning)
return object.__repr__(self)
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