author | martin.trojer@nokia.com |
Fri, 31 Jul 2009 15:01:17 +0100 | |
changeset 1 | 2fb8b9db1c86 |
permissions | -rw-r--r-- |
1
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
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changeset
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1 |
"""Example of a generator: re-implement the built-in range function |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
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without actually constructing the list of values. |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
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|
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
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parents:
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OldStyleRange is coded in the way required to work in a 'for' loop before |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
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parents:
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iterators were introduced into the language; using __getitem__ and __len__ . |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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parents:
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|
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Initial QEMU (symbian-qemu-0.9.1-12) import
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""" |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
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def handleargs(arglist): |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
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"""Take list of arguments and extract/create proper start, stop, and step |
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Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
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values and return in a tuple""" |
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Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
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11 |
try: |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
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if len(arglist) == 1: |
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Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
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return 0, int(arglist[0]), 1 |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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elif len(arglist) == 2: |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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15 |
return int(arglist[0]), int(arglist[1]), 1 |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
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elif len(arglist) == 3: |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
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if arglist[2] == 0: |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
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raise ValueError("step argument must not be zero") |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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return tuple(int(x) for x in arglist) |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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else: |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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raise TypeError("range() accepts 1-3 arguments, given", len(arglist)) |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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except TypeError: |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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raise TypeError("range() arguments must be numbers or strings " |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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"representing numbers") |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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|
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Initial QEMU (symbian-qemu-0.9.1-12) import
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def genrange(*a): |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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"""Function to implement 'range' as a generator""" |
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Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
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start, stop, step = handleargs(a) |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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value = start |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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while value < stop: |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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yield value |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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value += step |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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|
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Initial QEMU (symbian-qemu-0.9.1-12) import
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class oldrange: |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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"""Class implementing a range object. |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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To the user the instances feel like immutable sequences |
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Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
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(and you can't concatenate or slice them) |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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|
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
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Done using the old way (pre-iterators; __len__ and __getitem__) to have an |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
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object be used by a 'for' loop. |
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Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
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|
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Initial QEMU (symbian-qemu-0.9.1-12) import
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""" |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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|
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Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
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def __init__(self, *a): |
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Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
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""" Initialize start, stop, and step values along with calculating the |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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nubmer of values (what __len__ will return) in the range""" |
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Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
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self.start, self.stop, self.step = handleargs(a) |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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self.len = max(0, (self.stop - self.start) // self.step) |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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|
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Initial QEMU (symbian-qemu-0.9.1-12) import
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def __repr__(self): |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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"""implement repr(x) which is also used by print""" |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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return 'range(%r, %r, %r)' % (self.start, self.stop, self.step) |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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|
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Initial QEMU (symbian-qemu-0.9.1-12) import
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def __len__(self): |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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"""implement len(x)""" |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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return self.len |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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|
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Initial QEMU (symbian-qemu-0.9.1-12) import
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def __getitem__(self, i): |
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Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
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"""implement x[i]""" |
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Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
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if 0 <= i <= self.len: |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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return self.start + self.step * i |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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else: |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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raise IndexError, 'range[i] index out of range' |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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|
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Initial QEMU (symbian-qemu-0.9.1-12) import
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|
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
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def test(): |
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Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
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import time, __builtin__ |
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Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
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#Just a quick sanity check |
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Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
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correct_result = __builtin__.range(5, 100, 3) |
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Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
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oldrange_result = list(oldrange(5, 100, 3)) |
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Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
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genrange_result = list(genrange(5, 100, 3)) |
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Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
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if genrange_result != correct_result or oldrange_result != correct_result: |
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Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
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raise Exception("error in implementation:\ncorrect = %s" |
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Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
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"\nold-style = %s\ngenerator = %s" % |
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Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
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(correct_result, oldrange_result, genrange_result)) |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
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print "Timings for range(1000):" |
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Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
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t1 = time.time() |
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Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
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for i in oldrange(1000): |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
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pass |
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Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
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80 |
t2 = time.time() |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
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for i in genrange(1000): |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
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pass |
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Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
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t3 = time.time() |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
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for i in __builtin__.range(1000): |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
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pass |
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Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
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t4 = time.time() |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
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print t2-t1, 'sec (old-style class)' |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
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print t3-t2, 'sec (generator)' |
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Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
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print t4-t3, 'sec (built-in)' |
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Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
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|
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Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
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91 |
|
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Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
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if __name__ == '__main__': |
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Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
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test() |