ubelt.util_mixins module

This module defines the 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, have your object inherit from NiceRepr. To customize, define the __nice__ method.

Example

>>> # Objects that define __nice__ have a default __str__ and __repr__
>>> import ubelt as ub
>>> class Student(ub.NiceRepr):
...    def __init__(self, name):
...        self.name = name
...    def __nice__(self):
...        return self.name
>>> s1 = Student('Alice')
>>> s2 = Student('Bob')
>>> # The __str__ representation looks nice
>>> print('s1 = {}'.format(s1))
>>> print('s2 = {}'.format(s2))
s1 = <Student(Alice)>
s2 = <Student(Bob)>
>>> # xdoctest: +IGNORE_WANT
>>> # The __repr__ representation also looks nice
>>> print('s1 = {!r}'.format(s1))
>>> print('s2 = {!r}'.format(s2))
s1 = <Student(Alice) at 0x7f2c5460aad0>
s2 = <Student(Bob) at 0x7f2c5460ad10>

Example

>>> # Objects that define __len__ have a default __nice__
>>> import ubelt as ub
>>> class Group(ub.NiceRepr):
...    def __init__(self, data):
...        self.data = data
...    def __len__(self):
...        return len(self.data)
>>> g = Group([1, 2, 3])
>>> print('g = {}'.format(g))
g = <Group(3)>

class ubelt.util_mixins.NiceRepr

Bases: 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 NiceRepr should redefine __nice__. If the inheriting class has a __len__, method then the default __nice__ method will return its length.

Example

>>> import ubelt as ub
>>> class Foo(ub.NiceRepr):
...    def __nice__(self):
...        return 'info'
>>> foo = Foo()
>>> assert str(foo) == '<Foo(info)>'
>>> assert repr(foo).startswith('<Foo(info) at ')

Example

>>> import ubelt as ub
>>> class Bar(ub.NiceRepr):
...    pass
>>> bar = Bar()
>>> import pytest
>>> with pytest.warns(RuntimeWarning) as record:
>>>     assert 'object at' in str(bar)
>>>     assert 'object at' in repr(bar)

Example

>>> import ubelt as ub
>>> class Baz(ub.NiceRepr):
...    def __len__(self):
...        return 5
>>> baz = Baz()
>>> assert str(baz) == '<Baz(5)>'

Example

>>> import ubelt as ub
>>> # If your nice message has a bug, it shouldn't bring down the house
>>> class Foo(ub.NiceRepr):
...    def __nice__(self):
...        assert False
>>> foo = Foo()
>>> import pytest
>>> with pytest.warns(RuntimeWarning) as record:
>>>     print('foo = {!r}'.format(foo))
foo = <...Foo ...>

Example

>>> import ubelt as ub
>>> class Animal(ub.NiceRepr):
...    def __init__(self):
...        ...
...    def __nice__(self):
...        return ''
>>> class Cat(Animal):
>>>     ...
>>> class Dog(Animal):
>>>     ...
>>> class Beagle(Dog):
>>>     ...
>>> class Ragdoll(Cat):
>>>     ...
>>> instances = [Animal(), Cat(), Dog(), Beagle(), Ragdoll()]
>>> for inst in instances:
>>>     print(str(inst))
<Animal()>
<Cat()>
<Dog()>
<Beagle()>
<Ragdoll()>