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 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     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 

   150 Make 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 

   156 Generators 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 

   173 Generators 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 

   182 Verify 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 

   194 Verify 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 

   212 Make 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 

   217 Check 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 

   230 Check the __iter__ slot is defined to return self

   231 

   232     >>> iter(g) is g

   233     True

   234 

   235 Verify 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 

   246 Verify 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 

   263 def 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 

   279 if __name__ == "__main__":

   280     test_main(verbose=True)