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List comprehensions: Difference between revisions
→{{header|Python}}
Line 1,686:
<lang python>((x,y,z) for x in xrange(1,n+1) for y in xrange(x,n+1) for z in xrange(y,n+1) if x**2 + y**2 == z**2)</lang>
A slower but more readable version:
<lang python>[(x, y, z) for (x, y, z) in itertools.product(xrange(1,n+1),repeat=3) if x**2 + y**2 == z**2 and x <= y <= z]</lang>
Or as an iterator:
<lang python>((x, y, z) for (x, y, z) in itertools.product(xrange(1,n+1),repeat=3) if x**2 + y**2 == z**2 and x <= y <= z)</lang>
Alternatively we shorten the initial list comprehension but this time without compromising on speed. First we introduce a generator which generates all triplets:
<lang python>def triplets(n):
for x in xrange(1, n + 1):
for y in xrange(x, n + 1):
for z in xrange(y, n + 1):
yield x, y, z</lang>
Apply this to our list comprehension gives:
<lang python>[(x, y, z) for (x, y, z) in triplets(n) if x**2 + y**2 == z**2]</lang>
Or as an iterator:
<lang python>((x, y, z) for (x, y, z) in triplets(n) if x**2 + y**2 == z**2)</lang>
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