/Lib/test/test_genexps.py

  1doctests = """
  2
  3Test simple loop with conditional
  4
  5    >>> sum(i*i for i in range(100) if i&1 == 1)
  6    166650
  7
  8Test simple nesting
  9
 10    >>> list((i,j) for i in range(3) for j in range(4) )
 11    [(0, 0), (0, 1), (0, 2), (0, 3), (1, 0), (1, 1), (1, 2), (1, 3), (2, 0), (2, 1), (2, 2), (2, 3)]
 12
 13Test nesting with the inner expression dependent on the outer
 14
 15    >>> list((i,j) for i in range(4) for j in range(i) )
 16    [(1, 0), (2, 0), (2, 1), (3, 0), (3, 1), (3, 2)]
 17
 18Make sure the induction variable is not exposed
 19
 20    >>> i = 20
 21    >>> sum(i*i for i in range(100))
 22    328350
 23    >>> i
 24    20
 25
 26Test first class
 27
 28    >>> g = (i*i for i in range(4))
 29    >>> type(g)
 30    <type 'generator'>
 31    >>> list(g)
 32    [0, 1, 4, 9]
 33
 34Test direct calls to next()
 35
 36    >>> g = (i*i for i in range(3))
 37    >>> g.next()
 38    0
 39    >>> g.next()
 40    1
 41    >>> g.next()
 42    4
 43    >>> g.next()
 44    Traceback (most recent call last):
 45      File "<pyshell#21>", line 1, in -toplevel-
 46        g.next()
 47    StopIteration
 48
 49Does it stay stopped?
 50
 51    >>> g.next()
 52    Traceback (most recent call last):
 53      File "<pyshell#21>", line 1, in -toplevel-
 54        g.next()
 55    StopIteration
 56    >>> list(g)
 57    []
 58
 59Test running gen when defining function is out of scope
 60
 61    >>> def f(n):
 62    ...     return (i*i for i in xrange(n))
 63    >>> list(f(10))
 64    [0, 1, 4, 9, 16, 25, 36, 49, 64, 81]
 65
 66    >>> def f(n):
 67    ...     return ((i,j) for i in xrange(3) for j in xrange(n))
 68    >>> list(f(4))
 69    [(0, 0), (0, 1), (0, 2), (0, 3), (1, 0), (1, 1), (1, 2), (1, 3), (2, 0), (2, 1), (2, 2), (2, 3)]
 70    >>> def f(n):
 71    ...     return ((i,j) for i in xrange(3) for j in xrange(4) if j in xrange(n))
 72    >>> list(f(4))
 73    [(0, 0), (0, 1), (0, 2), (0, 3), (1, 0), (1, 1), (1, 2), (1, 3), (2, 0), (2, 1), (2, 2), (2, 3)]
 74    >>> list(f(2))
 75    [(0, 0), (0, 1), (1, 0), (1, 1), (2, 0), (2, 1)]
 76
 77Verify that parenthesis are required in a statement
 78
 79    >>> def f(n):
 80    ...     return i*i for i in xrange(n)
 81    Traceback (most recent call last):
 82       ...
 83    SyntaxError: invalid syntax
 84
 85Verify that parenthesis are required when used as a keyword argument value
 86
 87    >>> dict(a = i for i in xrange(10))
 88    Traceback (most recent call last):
 89       ...
 90    SyntaxError: invalid syntax
 91
 92Verify that parenthesis are required when used as a keyword argument value
 93
 94    >>> dict(a = (i for i in xrange(10))) #doctest: +ELLIPSIS
 95    {'a': <generator object <genexpr> at ...>}
 96
 97Verify early binding for the outermost for-expression
 98
 99    >>> x=10
100    >>> g = (i*i for i in range(x))
101    >>> x = 5
102    >>> list(g)
103    [0, 1, 4, 9, 16, 25, 36, 49, 64, 81]
104
105Verify that the outermost for-expression makes an immediate check
106for iterability
107
108    >>> (i for i in 6)
109    Traceback (most recent call last):
110      File "<pyshell#4>", line 1, in -toplevel-
111        (i for i in 6)
112    TypeError: 'int' object is not iterable
113
114Verify late binding for the outermost if-expression
115
116    >>> include = (2,4,6,8)
117    >>> g = (i*i for i in range(10) if i in include)
118    >>> include = (1,3,5,7,9)
119    >>> list(g)
120    [1, 9, 25, 49, 81]
121
122Verify late binding for the innermost for-expression
123
124    >>> g = ((i,j) for i in range(3) for j in range(x))
125    >>> x = 4
126    >>> list(g)
127    [(0, 0), (0, 1), (0, 2), (0, 3), (1, 0), (1, 1), (1, 2), (1, 3), (2, 0), (2, 1), (2, 2), (2, 3)]
128
129Verify re-use of tuples (a side benefit of using genexps over listcomps)
130
131    >>> tupleids = map(id, ((i,i) for i in xrange(10)))
132    >>> int(max(tupleids) - min(tupleids))
133    0
134
135Verify that syntax error's are raised for genexps used as lvalues
136
137    >>> (y for y in (1,2)) = 10
138    Traceback (most recent call last):
139       ...
140    SyntaxError: can't assign to generator expression (<doctest test.test_genexps.__test__.doctests[40]>, line 1)
141
142    >>> (y for y in (1,2)) += 10
143    Traceback (most recent call last):
144       ...
145    SyntaxError: augmented assignment to generator expression not possible (<doctest test.test_genexps.__test__.doctests[41]>, line 1)
146
147
148########### Tests borrowed from or inspired by test_generators.py ############
149
150Make a generator that acts like range()
151
152    >>> yrange = lambda n:  (i for i in xrange(n))
153    >>> list(yrange(10))
154    [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
155
156Generators always return to the most recent caller:
157
158    >>> def creator():
159    ...     r = yrange(5)
160    ...     print "creator", r.next()
161    ...     return r
162    >>> def caller():
163    ...     r = creator()
164    ...     for i in r:
165    ...             print "caller", i
166    >>> caller()
167    creator 0
168    caller 1
169    caller 2
170    caller 3
171    caller 4
172
173Generators can call other generators:
174
175    >>> def zrange(n):
176    ...     for i in yrange(n):
177    ...         yield i
178    >>> list(zrange(5))
179    [0, 1, 2, 3, 4]
180
181
182Verify that a gen exp cannot be resumed while it is actively running:
183
184    >>> g = (me.next() for i in xrange(10))
185    >>> me = g
186    >>> me.next()
187    Traceback (most recent call last):
188      File "<pyshell#30>", line 1, in -toplevel-
189        me.next()
190      File "<pyshell#28>", line 1, in <generator expression>
191        g = (me.next() for i in xrange(10))
192    ValueError: generator already executing
193
194Verify exception propagation
195
196    >>> g = (10 // i for i in (5, 0, 2))
197    >>> g.next()
198    2
199    >>> g.next()
200    Traceback (most recent call last):
201      File "<pyshell#37>", line 1, in -toplevel-
202        g.next()
203      File "<pyshell#35>", line 1, in <generator expression>
204        g = (10 // i for i in (5, 0, 2))
205    ZeroDivisionError: integer division or modulo by zero
206    >>> g.next()
207    Traceback (most recent call last):
208      File "<pyshell#38>", line 1, in -toplevel-
209        g.next()
210    StopIteration
211
212Make sure that None is a valid return value
213
214    >>> list(None for i in xrange(10))
215    [None, None, None, None, None, None, None, None, None, None]
216
217Check that generator attributes are present
218
219    >>> g = (i*i for i in range(3))
220    >>> expected = set(['gi_frame', 'gi_running', 'next'])
221    >>> set(attr for attr in dir(g) if not attr.startswith('__')) >= expected
222    True
223
224    >>> print g.next.__doc__
225    x.next() -> the next value, or raise StopIteration
226    >>> import types
227    >>> isinstance(g, types.GeneratorType)
228    True
229
230Check the __iter__ slot is defined to return self
231
232    >>> iter(g) is g
233    True
234
235Verify that the running flag is set properly
236
237    >>> g = (me.gi_running for i in (0,1))
238    >>> me = g
239    >>> me.gi_running
240    0
241    >>> me.next()
242    1
243    >>> me.gi_running
244    0
245
246Verify that genexps are weakly referencable
247
248    >>> import weakref
249    >>> g = (i*i for i in range(4))
250    >>> wr = weakref.ref(g)
251    >>> wr() is g
252    True
253    >>> p = weakref.proxy(g)
254    >>> list(p)
255    [0, 1, 4, 9]
256
257
258"""
259
260
261__test__ = {'doctests' : doctests}
262
263def test_main(verbose=None):
264    import sys
265    from test import test_support
266    from test import test_genexps
267    test_support.run_doctest(test_genexps, verbose)
268
269    # verify reference counting
270    if verbose and hasattr(sys, "gettotalrefcount"):
271        import gc
272        counts = [None] * 5
273        for i in xrange(len(counts)):
274            test_support.run_doctest(test_genexps, verbose)
275            gc.collect()
276            counts[i] = sys.gettotalrefcount()
277        print counts
278
279if __name__ == "__main__":
280    test_main(verbose=True)