87 lines
2.4 KiB
Plaintext
87 lines
2.4 KiB
Plaintext
The https://www.python.org/dev/peps/pep-0234/#python-api-specification[iterator protocol] specifies that an iterator object should have
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* a ``++__next__++`` method retrieving the next value or raising ``++StopIteration++`` when there are no more values left.
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* an ``++__iter__++`` method which should always return ``++self++``. This enables iterators to be used as sequences in for-loops and other places.
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This rule raises an issue when a class has a ``++__next__++`` method and either:
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* it doesn't have an ``++__iter__++`` method.
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* or its ``++__iter__++`` method does not return "self".
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== Noncompliant Code Example
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----
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class MyIterator: # Noncompliant. Class has a __next__ method but no __iter__ method
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def __init__(self, values):
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self._values = values
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self._index = 0
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def __next__(self):
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if self._index >= len(self._values):
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raise StopIteration()
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value = self._values[self._index]
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self._index += 1
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return value
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class MyIterator:
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def __init__(self, values):
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self._values = values
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self._index = 0
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def __next__(self):
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if self._index >= len(self._values):
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raise StopIteration()
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value = self._values[self._index]
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self._index += 1
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return value
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def __iter__(self):
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return 42 # Noncompliant. This __iter__ method does not return self
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class MyIterable: # Ok. This is an iterable, not an iterator, i.e. it has an __iter__ method but no __next__ method. Thus __iter__ doesn't have to return "self"
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def __init__(self, values):
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self._values = values
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def __iter__(self):
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return MyIterator(self._values)
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----
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== Compliant Solution
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----
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class MyIterator:
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def __init__(self, values):
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self._values = values
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self._index = 0
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def __next__(self):
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if self._index >= len(self._values):
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raise StopIteration()
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value = self._values[self._index]
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self._index += 1
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return value
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def __iter__(self):
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return self
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class MyIterable:
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def __init__(self, values):
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self._values = values
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def __iter__(self):
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return MyIterator(self._values)
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----
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== See
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* https://www.python.org/dev/peps/pep-0234/#python-api-specification[PEP 234 - Iterators]
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* https://docs.python.org/3/library/stdtypes.html#iterator-types[Python documentation - Iterator Types]
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