pairs from a list

[Matthew_WARREN at bnpparibas.com]

I'm just fiddling with this, am no great expert, but I added

def pairs5(x):
        o=[]
        for n in zip(x[::2],x[1:2]):
                o.append(n)
        return o

I dont know if that breaks any constraints placed on the problem, but I get
the following output

0.07158942896 0.266009705575 0.21342143313 0.0537146193457 0.0107680502972


does that make it faster than pairs(4) or am I breaking some constraints on
the problem?



Matt.





                                                                                                                                        
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Arnaud Delobelle wrote:
> pairs4 wins.


Oops. I see a smaller difference,
but yes, pairs4 wins.

Alan Isaac

import time
from itertools import islice, izip

x = range(500001)

def pairs1(x):
    return izip(islice(x,0,None,2),islice(x,1,None,2))

def pairs2(x):
    xiter = iter(x)
    while True:
        yield xiter.next(), xiter.next()

def pairs3(x):
    for i in range( len(x)//2 ):
        yield x[2*i], x[2*i+1],

def pairs4(x):
    xiter = iter(x)
    return izip(xiter,xiter)

t = time.clock()
for x1, x2 in pairs1(x):
    pass
t1 = time.clock() - t

t = time.clock()
for x1, x2 in pairs2(x):
    pass
t2 = time.clock() - t

t = time.clock()
for x1, x2 in pairs3(x):
    pass
t3 = time.clock() - t

t = time.clock()
for x1, x2 in pairs4(x):
    pass
t4 = time.clock() - t

print t1, t2, t3, t4

Output:
0.317524154606 1.13436847421 1.07100930426 0.262926712753
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