cython

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import cython
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class Unhashable(object):
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    def __hash__(self):
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        raise TypeError('I am not hashable')
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class Hashable(object):
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    def __hash__(self):
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        return 1
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    def __eq__(self, other):
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        return isinstance(other, Hashable)
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class CountedHashable(object):
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    def __init__(self):
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        self.hash_count = 0
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        self.eq_count = 0
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    def __hash__(self):
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        self.hash_count += 1
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        return 42
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    def __eq__(self, other):
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        self.eq_count += 1
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        return id(self) == id(other)
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@cython.test_fail_if_path_exists('//AttributeNode')
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@cython.test_assert_path_exists('//PythonCapiCallNode')
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@cython.locals(d=dict)
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def setdefault1(d, key):
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    """
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    >>> d = {}
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    >>> setdefault1(d, 1)
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    >>> len(d)
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    1
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    >>> setdefault1(d, 1)
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    >>> len(d)
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    1
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    >>> d[1]
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    >>> setdefault1(d, Unhashable())
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    Traceback (most recent call last):
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    TypeError: I am not hashable
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    >>> len(d)
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    1
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    >>> h1 = setdefault1(d, Hashable())
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    >>> len(d)
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    2
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    >>> h2 = setdefault1(d, Hashable())
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    >>> len(d)
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    2
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    >>> d[Hashable()]
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    # CPython's behaviour depends on version and py_debug setting, so just compare to it
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    >>> py_hashed1 = CountedHashable()
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    >>> y = {py_hashed1: 5}
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    >>> py_hashed2 = CountedHashable()
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    >>> y.setdefault(py_hashed2)
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    >>> cy_hashed1 = CountedHashable()
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    >>> y = {cy_hashed1: 5}
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    >>> cy_hashed2 = CountedHashable()
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    >>> setdefault1(y, cy_hashed2)
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    >>> py_hashed1.hash_count - cy_hashed1.hash_count
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    0
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    >>> py_hashed2.hash_count - cy_hashed2.hash_count
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    0
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    >>> (py_hashed1.eq_count + py_hashed2.eq_count) - (cy_hashed1.eq_count + cy_hashed2.eq_count)
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    0
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    """
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    return d.setdefault(key)
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@cython.test_fail_if_path_exists('//AttributeNode')
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@cython.test_assert_path_exists('//PythonCapiCallNode')
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@cython.locals(d=dict)
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def setdefault2(d, key, value):
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    """
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    >>> d = {}
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    >>> setdefault2(d, 1, 2)
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    2
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    >>> len(d)
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    1
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    >>> setdefault2(d, 1, 2)
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    2
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    >>> len(d)
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    1
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    >>> l = setdefault2(d, 2, [])
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    >>> len(d)
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    2
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    >>> l.append(1)
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    >>> setdefault2(d, 2, [])
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    [1]
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    >>> len(d)
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    2
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    >>> setdefault2(d, Unhashable(), 1)
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    Traceback (most recent call last):
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    TypeError: I am not hashable
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    >>> h1 = setdefault2(d, Hashable(), 55)
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    >>> len(d)
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    3
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    >>> h2 = setdefault2(d, Hashable(), 66)
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    >>> len(d)
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    3
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    >>> d[Hashable()]
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    55
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    # CPython's behaviour depends on version and py_debug setting, so just compare to it
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    >>> py_hashed1 = CountedHashable()
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    >>> y = {py_hashed1: 5}
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    >>> py_hashed2 = CountedHashable()
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    >>> y.setdefault(py_hashed2, [])
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    []
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    >>> cy_hashed1 = CountedHashable()
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    >>> y = {cy_hashed1: 5}
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    >>> cy_hashed2 = CountedHashable()
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    >>> setdefault2(y, cy_hashed2, [])
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    []
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    >>> py_hashed1.hash_count - cy_hashed1.hash_count
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    0
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    >>> py_hashed2.hash_count - cy_hashed2.hash_count
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    0
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    >>> (py_hashed1.eq_count + py_hashed2.eq_count) - (cy_hashed1.eq_count + cy_hashed2.eq_count)
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    0
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    """
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    return d.setdefault(key, value)
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