doctests = """

Test simple loop with conditional

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

    166650

Test simple nesting

    >>> list((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((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

Test first class

    >>> g = (i*i for i in range(4))

    >>> type(g)

    <type 'generator'>

    >>> list(g)

    [0, 1, 4, 9]

Test direct calls to next()

    >>> g = (i*i for i in range(3))

    >>> g.next()

    0

    >>> g.next()

    1

    >>> g.next()

    4

    >>> g.next()

    Traceback (most recent call last):

      File "<pyshell#21>", line 1, in -toplevel-

        g.next()

    StopIteration

Does it stay stopped?

    >>> g.next()

    Traceback (most recent call last):

      File "<pyshell#21>", line 1, in -toplevel-

        g.next()

    StopIteration

    >>> list(g)

    []

Test running gen when defining function is out of scope

    >>> def f(n):

    ...     return (i*i for i in xrange(n))

    >>> list(f(10))

    [0, 1, 4, 9, 16, 25, 36, 49, 64, 81]

    >>> def f(n):

    ...     return ((i,j) for i in xrange(3) for j in xrange(n))

    >>> list(f(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)]

    >>> def f(n):

    ...     return ((i,j) for i in xrange(3) for j in xrange(4) if j in xrange(n))

    >>> list(f(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)]

    >>> list(f(2))

    [(0, 0), (0, 1), (1, 0), (1, 1), (2, 0), (2, 1)]

Verify that parenthesis are required in a statement

    >>> def f(n):

    ...     return i*i for i in xrange(n)

    Traceback (most recent call last):

       ...

    SyntaxError: invalid syntax

Verify that parenthesis are required when used as a keyword argument value

    >>> dict(a = i for i in xrange(10))

    Traceback (most recent call last):

       ...

    SyntaxError: invalid syntax

Verify that parenthesis are required when used as a keyword argument value

    >>> dict(a = (i for i in xrange(10))) #doctest: +ELLIPSIS

    {'a': <generator object at ...>}

Verify early binding for the outermost for-expression

    >>> x=10

    >>> g = (i*i for i in range(x))

    >>> x = 5

    >>> list(g)

    [0, 1, 4, 9, 16, 25, 36, 49, 64, 81]

Verify that the outermost for-expression makes an immediate check

for iterability

    >>> (i for i in 6)

    Traceback (most recent call last):

      File "<pyshell#4>", line 1, in -toplevel-

        (i for i in 6)

    TypeError: 'int' object is not iterable

Verify late binding for the outermost if-expression

    >>> include = (2,4,6,8)

    >>> g = (i*i for i in range(10) if i in include)

    >>> include = (1,3,5,7,9)

    >>> list(g)

    [1, 9, 25, 49, 81]

Verify late binding for the innermost for-expression

    >>> g = ((i,j) for i in range(3) for j in range(x))

    >>> x = 4

    >>> list(g)

    [(0, 0), (0, 1), (0, 2), (0, 3), (1, 0), (1, 1), (1, 2), (1, 3), (2, 0), (2, 1), (2, 2), (2, 3)]

Verify re-use of tuples (a side benefit of using genexps over listcomps)

    >>> tupleids = map(id, ((i,i) for i in xrange(10)))

    >>> int(max(tupleids) - min(tupleids))

    0

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

    >>> (y for y in (1,2)) = 10

    Traceback (most recent call last):

       ...

    SyntaxError: can't assign to generator expression (<doctest test.test_genexps.__test__.doctests[40]>, line 1)

    >>> (y for y in (1,2)) += 10

    Traceback (most recent call last):

       ...

    SyntaxError: augmented assignment to generator expression not possible (<doctest test.test_genexps.__test__.doctests[41]>, line 1)

########### Tests borrowed from or inspired by test_generators.py ############

Make a generator that acts like range()

    >>> yrange = lambda n:  (i for i in xrange(n))

    >>> list(yrange(10))

    [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

Generators always return to the most recent caller:

    >>> def creator():

    ...     r = yrange(5)

    ...     print "creator", r.next()

    ...     return r

    >>> def caller():

    ...     r = creator()

    ...     for i in r:

    ...             print "caller", i

    >>> caller()

    creator 0

    caller 1

    caller 2

    caller 3

    caller 4

Generators can call other generators:

    >>> def zrange(n):

    ...     for i in yrange(n):

    ...         yield i

    >>> list(zrange(5))

    [0, 1, 2, 3, 4]

Verify that a gen exp cannot be resumed while it is actively running:

    >>> g = (me.next() for i in xrange(10))

    >>> me = g

    >>> me.next()

    Traceback (most recent call last):

      File "<pyshell#30>", line 1, in -toplevel-

        me.next()

      File "<pyshell#28>", line 1, in <generator expression>

        g = (me.next() for i in xrange(10))

    ValueError: generator already executing

Verify exception propagation

    >>> g = (10 // i for i in (5, 0, 2))

    >>> g.next()

    2

    >>> g.next()

    Traceback (most recent call last):

      File "<pyshell#37>", line 1, in -toplevel-

        g.next()

      File "<pyshell#35>", line 1, in <generator expression>

        g = (10 // i for i in (5, 0, 2))

    ZeroDivisionError: integer division or modulo by zero

    >>> g.next()

    Traceback (most recent call last):

      File "<pyshell#38>", line 1, in -toplevel-

        g.next()

    StopIteration

Make sure that None is a valid return value

    >>> list(None for i in xrange(10))

    [None, None, None, None, None, None, None, None, None, None]

Check that generator attributes are present

    >>> g = (i*i for i in range(3))

    >>> expected = set(['gi_frame', 'gi_running', 'next'])

    >>> set(attr for attr in dir(g) if not attr.startswith('__')) >= expected

    True

    >>> print g.next.__doc__

    x.next() -> the next value, or raise StopIteration

    >>> import types

    >>> isinstance(g, types.GeneratorType)

    True

Check the __iter__ slot is defined to return self

    >>> iter(g) is g

    True

Verify that the running flag is set properly

    >>> g = (me.gi_running for i in (0,1))

    >>> me = g

    >>> me.gi_running

    0

    >>> me.next()

    1

    >>> me.gi_running

    0

Verify that genexps are weakly referencable

    >>> import weakref

    >>> g = (i*i for i in range(4))

    >>> wr = weakref.ref(g)

    >>> wr() is g

    True

    >>> p = weakref.proxy(g)

    >>> list(p)

    [0, 1, 4, 9]

"""

__test__ = {'doctests' : doctests}

def test_main(verbose=None):

    import sys

    from test import test_support

    from test import test_genexps

    test_support.run_doctest(test_genexps, verbose)

    # verify reference counting

    if verbose and hasattr(sys, "gettotalrefcount"):

        import gc

        counts = [None] * 5

        for i in xrange(len(counts)):

            test_support.run_doctest(test_genexps, verbose)

            gc.collect()

            counts[i] = sys.gettotalrefcount()

        print counts

if __name__ == "__main__":

    test_main(verbose=True)