53 lines
1.3 KiB
ReStructuredText
53 lines
1.3 KiB
ReStructuredText
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.. _why:
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Why?
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====
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The difference between namedtuple_\ s and classes decorated by ``characteristic`` is that the latter are type-sensitive and less typing aside regular classes:
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.. doctest::
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>>> from characteristic import Attribute, attributes
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>>> @attributes
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... class C1(object):
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... a = Attribute()
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... def __init__(self):
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... if not isinstance(self.a, int):
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... raise ValueError("'a' must be an integer.")
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... def print_a(self):
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... print self.a
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>>> @attributes
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... class C2(object):
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... a = Attribute()
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>>> c1 = C1(a=1)
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>>> c2 = C2(a=1)
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>>> c1 == c2
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False
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>>> c1.print_a()
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1
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>>> C1(a="hello")
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Traceback (most recent call last):
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...
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ValueError: 'a' must be an integer.
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…while namedtuple’s purpose is *explicitly* to behave like tuples:
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.. doctest::
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>>> from collections import namedtuple
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>>> NT1 = namedtuple("NT1", "a")
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>>> NT2 = namedtuple("NT2", "b")
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>>> t1 = NT1._make([1,])
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>>> t2 = NT2._make([1,])
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>>> t1 == t2 == (1,)
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True
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This can easily lead to surprising and unintended behaviors.
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.. _namedtuple: https://docs.python.org/2/library/collections.html#collections.namedtuple
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.. _tuple: https://docs.python.org/2/tutorial/datastructures.html#tuples-and-sequences
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