Felipe
I get the same results as you. You make a good point about not
iterating when it's not needed. I played around with your test code
and found some interesting things:
1. enumerate vs. range(len()) has very little overhead (something I
have wondered about)
In my code, making the change causes the timing to go from 27.5 usec to
24.6 usec: basically nothing.
2. I combined the two result statements into one, and your code as
written still appears consistently faster, albeit only slightly:
One-line assignment to result: 6.98; 7.18; 6.49; 7.1 (code below)
Your way via extend: 5.24; 5.26; 5.09; 5.3; 5.26; 5.21 (code further
below)
Is this because of "+" concatenation?
My one-line assignment to result:
[EMAIL PROTECTED] ~]$ python2.4 -mtimeit -s "def shift(lst, n): length =
len(lst); first =(-n) % length; result = list(lst[first:]) +
list(lst[:first]); return result"
"shift('abcdefghijklmnopqrstuvwxyz',2)" 100000 loops, best of 3: 6.98
usec per loop
[EMAIL PROTECTED] ~]$ python2.4 -mtimeit -s "def shift(lst, n): length =
len(lst); first =(-n) % length; result = list(lst[first:]) +
list(lst[:first]); return result"
"shift('abcdefghijklmnopqrstuvwxyz',2)"
100000 loops, best of 3: 7.18 usec per loop
[EMAIL PROTECTED] ~]$ python2.4 -mtimeit -s "def shift(lst, n): length =
len(lst); first =(-n) % length; result = list(lst[first:]) +
list(lst[:first]); return result"
"shift('abcdefghijklmnopqrstuvwxyz',2)"
100000 loops, best of 3: 6.49 usec per loop
[EMAIL PROTECTED] ~]$ python2.4 -mtimeit -s "def shift(lst, n): length =
len(lst); first =(-n) % length; result = list(lst[first:]) +
list(lst[:first]); return result"
"shift('abcdefghijklmnopqrstuvwxyz',2)"
100000 loops, best of 3: 7.1 usec per loop
Your code:
[EMAIL PROTECTED] ~]$ python2.4 -mtimeit -s "def shift(lst, n): length =
len(lst); first =(-n) % length; result = list(lst[first:]);
result.extend(lst[:first]); return result"
"shift('abcdefghijklmnopqrstuvwxyz',2)"
100000 loops, best of 3: 5.24 usec per loop
[EMAIL PROTECTED] ~]$ python2.4 -mtimeit -s "def shift(lst, n): length =
len(lst); first =(-n) % length; result = list(lst[first:]);
result.extend(lst[:first]); return result"
"shift('abcdefghijklmnopqrstuvwxyz',2)"
100000 loops, best of 3: 5.26 usec per loop
[EMAIL PROTECTED] ~]$ python2.4 -mtimeit -s "def shift(lst, n): length =
len(lst); first =(-n) % length; result = list(lst[first:]);
result.extend(lst[:first]); return result"
"shift('abcdefghijklmnopqrstuvwxyz',2)"
100000 loops, best of 3: 5.09 usec per loop
[EMAIL PROTECTED] ~]$ python2.4 -mtimeit -s "def shift(lst, n): length =
len(lst); first =(-n) % length; result = list(lst[first:]);
result.extend(lst[:first]); return result"
"shift('abcdefghijklmnopqrstuvwxyz',2)"
100000 loops, best of 3: 5.3 usec per loop
[EMAIL PROTECTED] ~]$ python2.4 -mtimeit -s "def shift(lst, n): length =
len(lst); first =(-n) % length; result = list(lst[first:]);
result.extend(lst[:first]); return result"
"shift('abcdefghijklmnopqrstuvwxyz',2)"
100000 loops, best of 3: 5.26 usec per loop
[EMAIL PROTECTED] ~]$ python2.4 -mtimeit -s "def shift(lst, n): length =
len(lst); first =(-n) % length; result = list(lst[first:]);
result.extend(lst[:first]); return result"
"shift('abcdefghijklmnopqrstuvwxyz',2)"
100000 loops, best of 3: 5.21 usec per loop
Caleb
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