Viewing file:  test_genexps.py (6.99 KB) -rw-r--r--
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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: iteration over non-sequence
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)))
>>> 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: assign to generator expression not possible
>>> (y for y in (1,2)) += 10
Traceback (most recent call last):
...
SyntaxError: augmented assign to tuple literal or generator expression not possible
########### 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)
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