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To: python-list@python.org
From: "Frank Millman" <frank@chagford.com>
Subject: Re: Dict comprehensions - improvement to docs?
Date: Mon, 16 Mar 2015 11:01:22 +0200
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"Paul Rubin" <no.email@nospam.invalid> wrote in message 
news:87wq2hfibu.fsf@jester.gateway.sonic.net...
> "Frank Millman" <frank@chagford.com> writes:
>> dict((a, b) for a, b in zip(x, y))
>> 100000 loops, best of 3: 16.1 usec per loop
>> {a: b for a, b in zip(x, y)}"
>> 100000 loops, best of 3: 6.38 usec per loop
>
> Hmm, I bet the difference is from the (a,b) consing all those tuples.
>
> Can you try just dict(zip(x,y))  ?

C:\>python -m timeit -s "x = range(65, 91); y = (chr(z) for z in x)" 
"dict(zip(x, y))"
100000 loops, best of 3: 11.9 usec per loop

C:\>python -m timeit -s "x = range(65, 91); y = (chr(z) for z in x)" "{a: b 
for a, b in zip(x, y)}"
100000 loops, best of 3: 7.24 usec per loop

I ran the dict comp again in case the machine load had changed - it is a bit 
slower, but not much.

Frank