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annotate python/example/factorial.py @ 838:3cda483d71b2

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author Jeff Hammel <k0scist@gmail.com>
date Fri, 31 Mar 2017 16:30:52 -0700
parents 47a434dd5068
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47a434dd5068 example: factorial using reduce
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1 #!/usr/bin/env python
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2 """how many 0s are in a factorial"""
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3
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4 import argparse
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5 import sys
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6
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7 def factorial(N):
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8 """factorial of `N`"""
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9 if N == 1:
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10 return 1
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11 return reduce(int.__mul__, range(2, N+1))
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12
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13 def factorial_zeros(N):
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14 """how many 0s are in a factorial?"""
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15
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16 return N/5
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17
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18 def main(args=sys.argv[1:]):
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19 """CLI"""
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20
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21 parser = argparse.ArgumentParser(description=__doc__)
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22 parser.add_argument('N', type=int, nargs='+')
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23 options = parser.parse_args(args)
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24
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25 # sanity
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26 if any([i < 1 for i in options.N]):
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27 parser.error("Input values must be >= 1")
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28
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29 for i in options.N:
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30 f = factorial(i)
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31 print f
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32
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33 if __name__ == '__main__':
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34 main()