# pypy-postgresql / lib-python / 2.7 / test / test_genexps.py

 ``` 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283``` ```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) >>> 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 "", line 1, in -toplevel- g.next() StopIteration Does it stay stopped? >>> g.next() Traceback (most recent call last): File "", 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': 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 "", 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) >>> from test.test_support import check_impl_detail >>> tupleids = map(id, ((i,i) for i in xrange(10))) >>> int(max(tupleids) - min(tupleids)) if check_impl_detail() else 0 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): ... File "", line 1 SyntaxError: can't assign to generator expression >>> (y for y in (1,2)) += 10 Traceback (most recent call last): ... File "", line 1 SyntaxError: can't assign to generator expression ########### 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 "", line 1, in -toplevel- me.next() File "", line 1, in 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() # doctest: +ELLIPSIS Traceback (most recent call last): File "", line 1, in -toplevel- g.next() File "", line 1, in g = (10 // i for i in (5, 0, 2)) ZeroDivisionError: integer division...by zero >>> g.next() Traceback (most recent call last): File "", 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) ```