view Lib/test/test_setcomps.py @ 87690:66c1c9f32567 default tip

Add use_weakref option to functools.lru_cache The use_weakref option makes lru_cache create weak references to the function arguments when creating the cache key, which prevents them from staying in the memory forever even after all other references to them are gone. This is a proof of concept for http://bugs.python.org/issue19859
author Radomir Dopieralski <devel@sheep.art.pl>
date Tue, 03 Dec 2013 16:02:48 +0100
parents 9c930a32cebb
children
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doctests = """
########### Tests mostly copied from test_listcomps.py ############

Test simple loop with conditional

    >>> sum({i*i for i in range(100) if i&1 == 1})
    166650

Test simple case

    >>> {2*y + x + 1 for x in (0,) for y in (1,)}
    {3}

Test simple nesting

    >>> list(sorted({(i,j) for i in range(3) for j in range(4)}))
    [(0, 0), (0, 1), (0, 2), (0, 3), (1, 0), (1, 1), (1, 2), (1, 3), (2, 0), (2, 1), (2, 2), (2, 3)]

Test nesting with the inner expression dependent on the outer

    >>> list(sorted({(i,j) for i in range(4) for j in range(i)}))
    [(1, 0), (2, 0), (2, 1), (3, 0), (3, 1), (3, 2)]

Make sure the induction variable is not exposed

    >>> i = 20
    >>> sum({i*i for i in range(100)})
    328350

    >>> i
    20

Verify that syntax error's are raised for setcomps used as lvalues

    >>> {y for y in (1,2)} = 10          # doctest: +IGNORE_EXCEPTION_DETAIL
    Traceback (most recent call last):
       ...
    SyntaxError: ...

    >>> {y for y in (1,2)} += 10         # doctest: +IGNORE_EXCEPTION_DETAIL
    Traceback (most recent call last):
       ...
    SyntaxError: ...


Make a nested set comprehension that acts like set(range())

    >>> def srange(n):
    ...     return {i for i in range(n)}
    >>> list(sorted(srange(10)))
    [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

Same again, only as a lambda expression instead of a function definition

    >>> lrange = lambda n:  {i for i in range(n)}
    >>> list(sorted(lrange(10)))
    [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

Generators can call other generators:

    >>> def grange(n):
    ...     for x in {i for i in range(n)}:
    ...         yield x
    >>> list(sorted(grange(5)))
    [0, 1, 2, 3, 4]


Make sure that None is a valid return value

    >>> {None for i in range(10)}
    {None}

########### Tests for various scoping corner cases ############

Return lambdas that use the iteration variable as a default argument

    >>> items = {(lambda i=i: i) for i in range(5)}
    >>> {x() for x in items} == set(range(5))
    True

Same again, only this time as a closure variable

    >>> items = {(lambda: i) for i in range(5)}
    >>> {x() for x in items}
    {4}

Another way to test that the iteration variable is local to the list comp

    >>> items = {(lambda: i) for i in range(5)}
    >>> i = 20
    >>> {x() for x in items}
    {4}

And confirm that a closure can jump over the list comp scope

    >>> items = {(lambda: y) for i in range(5)}
    >>> y = 2
    >>> {x() for x in items}
    {2}

We also repeat each of the above scoping tests inside a function

    >>> def test_func():
    ...     items = {(lambda i=i: i) for i in range(5)}
    ...     return {x() for x in items}
    >>> test_func() == set(range(5))
    True

    >>> def test_func():
    ...     items = {(lambda: i) for i in range(5)}
    ...     return {x() for x in items}
    >>> test_func()
    {4}

    >>> def test_func():
    ...     items = {(lambda: i) for i in range(5)}
    ...     i = 20
    ...     return {x() for x in items}
    >>> test_func()
    {4}

    >>> def test_func():
    ...     items = {(lambda: y) for i in range(5)}
    ...     y = 2
    ...     return {x() for x in items}
    >>> test_func()
    {2}

"""


__test__ = {'doctests' : doctests}

def test_main(verbose=None):
    import sys
    from test import support
    from test import test_setcomps
    support.run_doctest(test_setcomps, verbose)

    # verify reference counting
    if verbose and hasattr(sys, "gettotalrefcount"):
        import gc
        counts = [None] * 5
        for i in range(len(counts)):
            support.run_doctest(test_setcomps, verbose)
            gc.collect()
            counts[i] = sys.gettotalrefcount()
        print(counts)

if __name__ == "__main__":
    test_main(verbose=True)