[Tutor] How is the return statement working in this function?
Greg Christian
glchristian at comcast.net
Fri Apr 6 02:39:39 CEST 2012
I am just wondering if anyone can explain how the return statement in this function is working (the code is from activestate.com)? Where does x come from – it is not initialized anywhere else and then just appears in the return statement. Any help would be appreciated.
def primes(n):
"""Prime number generator up to n - (generates a list)"""
## {{{ http://code.activestate.com/recipes/366178/ (r5)
if n == 2: return [2]
elif n < 2: return []
s = range(3, n + 1, 2)
mroot = n ** 0.5
half = (n + 1)/2 - 1
i = 0
m = 3
while m <= mroot:
if s[i]:
j = (m * m - 3)/2
s[j] = 0
while j < half:
s[j] = 0
j += m
i = i + 1
m = 2 * i + 3
return [2]+[x for x in s if x]
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