6 examples of 'python n choose k' in Python

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def rchoose(n, k):
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    if 0 <= n < MAX and 0 <= k < MAX:
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        return C[n][k]
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    else:
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        return choose(n, k)

120
def choose(n, k):
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    if 0 <= k <= n:
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        ntok = 1
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        ktok = 1
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        for t in range(1, min(k, n - k) + 1):
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            ntok *= n
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            ktok *= t
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            n -= 1
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        return ntok / ktok
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    else:
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        return 0

1
def choose(n, k):
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    """
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    A fast way to calculate binomial coefficients by Andrew Dalke (contrib).
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    """
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    if 0 <= k <= n:
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        ntok = 1
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        ktok = 1
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        for t in xrange(1, min(k, n - k) + 1):
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            ntok *= n
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            ktok *= t
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            n -= 1
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        return ntok // ktok
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    else:
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        return 0

58
def a_choose_b(n,k):
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    return reduce(lambda a,b: a*(n-b)/(b+1),xrange(k),1)

8
def log_choose(n, k):
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    r = 0.0
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    # swap for efficiency if k is more than half of n
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    if k * 2 > n:
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        k = n - k
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    for  d in range(1,k+1):
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        r += numpy.log10(n)
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        r -= numpy.log10(d)
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        n -= 1
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    return r

24
def __init__(self, n, k):
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    """
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    TESTS::
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        sage: from sage.combinat.choose_nk import ChooseNK        
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        sage: c52 = ChooseNK(5,2)
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        sage: c52 == loads(dumps(c52))
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        True
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    """
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    self._n = n
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    self._k = k