Mercurial > cpython-lru_cache-weakref

annotate Demo/scripts/fact.py @ 80661:94de77bd0b4b 2.7

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Issue #16194: document imp.load_dynamic problems when read several extension modules from the same binary object file.
author Andrew Svetlov <andrew.svetlov@gmail.com>
date Thu, 29 Nov 2012 19:51:28 +0200
parents 6587ea6d3e78
children
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73758db2f464 /usr/local/bin/python -> /usr/bin/env python
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1 #! /usr/bin/env python
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2
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3 # Factorize numbers.
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4 # The algorithm is not efficient, but easy to understand.
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5 # If there are large factors, it will take forever to find them,
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6 # because we try all odd numbers between 3 and sqrt(n)...
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7
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8 import sys
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9 from math import sqrt
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10
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11 def fact(n):
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12 if n < 1:
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13 raise ValueError('fact() argument should be >= 1')
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14 if n == 1:
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15 return [] # special case
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16 res = []
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17 # Treat even factors special, so we can use i += 2 later
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18 while n % 2 == 0:
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19 res.append(2)
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20 n //= 2
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21 # Try odd numbers up to sqrt(n)
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22 limit = sqrt(n+1)
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23 i = 3
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24 while i <= limit:
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25 if n % i == 0:
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26 res.append(i)
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27 n //= i
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28 limit = sqrt(n+1)
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29 else:
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30 i += 2
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31 if n != 1:
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32 res.append(n)
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33 return res
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34
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35 def main():
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36 if len(sys.argv) > 1:
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37 source = sys.argv[1:]
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38 else:
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39 source = iter(raw_input, '')
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40 for arg in source:
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41 try:
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42 n = int(arg)
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43 except ValueError:
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44 print arg, 'is not an integer'
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45 else:
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46 print n, fact(n)
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47
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48 if __name__ == "__main__":
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49 main()