Lib/test/test_genexps.py

   1 doctests = """
   2
   3 Test simple loop with conditional
   4
   5     >>> sum(i*i for i in range(100) if i&1 == 1)
   6     166650
   7
   8 Test 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
  13 Test 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
  18 Make 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
  26 Test 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
  34 Test 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
  49 Does 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
  59 Test 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
  77 Verify 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
  85 Verify 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
  92 Verify 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
  97 Verify 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
 105 Verify that the outermost for-expression makes an immediate check
 106 for 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
 114 Verify 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
 122 Verify 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
 129 Verify 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
 135 Verify 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       File "<doctest test.test_genexps.__test__.doctests[40]>", line 1
 141     SyntaxError: can't assign to generator expression
 142
 143     >>> (y for y in (1,2)) += 10
 144     Traceback (most recent call last):
 145        ...
 146       File "<doctest test.test_genexps.__test__.doctests[41]>", line 1
 147     SyntaxError: can't assign to generator expression
 148
 149
 150 ########### Tests borrowed from or inspired by test_generators.py ############
 151
 152 Make a generator that acts like range()
 153
 154     >>> yrange = lambda n:  (i for i in xrange(n))
 155     >>> list(yrange(10))
 156     [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
 157
 158 Generators always return to the most recent caller:
 159
 160     >>> def creator():
 161     ...     r = yrange(5)
 162     ...     print "creator", r.next()
 163     ...     return r
 164     >>> def caller():
 165     ...     r = creator()
 166     ...     for i in r:
 167     ...             print "caller", i
 168     >>> caller()
 169     creator 0
 170     caller 1
 171     caller 2
 172     caller 3
 173     caller 4
 174
 175 Generators can call other generators:
 176
 177     >>> def zrange(n):
 178     ...     for i in yrange(n):
 179     ...         yield i
 180     >>> list(zrange(5))
 181     [0, 1, 2, 3, 4]
 182
 183
 184 Verify that a gen exp cannot be resumed while it is actively running:
 185
 186     >>> g = (me.next() for i in xrange(10))
 187     >>> me = g
 188     >>> me.next()
 189     Traceback (most recent call last):
 190       File "<pyshell#30>", line 1, in -toplevel-
 191         me.next()
 192       File "<pyshell#28>", line 1, in <generator expression>
 193         g = (me.next() for i in xrange(10))
 194     ValueError: generator already executing
 195
 196 Verify exception propagation
 197
 198     >>> g = (10 // i for i in (5, 0, 2))
 199     >>> g.next()
 200     2
 201     >>> g.next()
 202     Traceback (most recent call last):
 203       File "<pyshell#37>", line 1, in -toplevel-
 204         g.next()
 205       File "<pyshell#35>", line 1, in <generator expression>
 206         g = (10 // i for i in (5, 0, 2))
 207     ZeroDivisionError: integer division or modulo by zero
 208     >>> g.next()
 209     Traceback (most recent call last):
 210       File "<pyshell#38>", line 1, in -toplevel-
 211         g.next()
 212     StopIteration
 213
 214 Make sure that None is a valid return value
 215
 216     >>> list(None for i in xrange(10))
 217     [None, None, None, None, None, None, None, None, None, None]
 218
 219 Check that generator attributes are present
 220
 221     >>> g = (i*i for i in range(3))
 222     >>> expected = set(['gi_frame', 'gi_running', 'next'])
 223     >>> set(attr for attr in dir(g) if not attr.startswith('__')) >= expected
 224     True
 225
 226     >>> print g.next.__doc__
 227     x.next() -> the next value, or raise StopIteration
 228     >>> import types
 229     >>> isinstance(g, types.GeneratorType)
 230     True
 231
 232 Check the __iter__ slot is defined to return self
 233
 234     >>> iter(g) is g
 235     True
 236
 237 Verify that the running flag is set properly
 238
 239     >>> g = (me.gi_running for i in (0,1))
 240     >>> me = g
 241     >>> me.gi_running
 242     0
 243     >>> me.next()
 244     1
 245     >>> me.gi_running
 246     0
 247
 248 Verify that genexps are weakly referencable
 249
 250     >>> import weakref
 251     >>> g = (i*i for i in range(4))
 252     >>> wr = weakref.ref(g)
 253     >>> wr() is g
 254     True
 255     >>> p = weakref.proxy(g)
 256     >>> list(p)
 257     [0, 1, 4, 9]
 258
 259
 260 """
 261
 262
 263 __test__ = {'doctests' : doctests}
 264
 265 def test_main(verbose=None):
 266     import sys
 267     from test import test_support
 268     from test import test_genexps
 269     test_support.run_doctest(test_genexps, verbose)
 270
 271     # verify reference counting
 272     if verbose and hasattr(sys, "gettotalrefcount"):
 273         import gc
 274         counts = [None] * 5
 275         for i in xrange(len(counts)):
 276             test_support.run_doctest(test_genexps, verbose)
 277             gc.collect()
 278             counts[i] = sys.gettotalrefcount()
 279         print counts
 280
 281 if __name__ == "__main__":
 282     test_main(verbose=True)