jeremit0 wrote:
Steve Holden wrote:
If you want line numbers,. of course, then you can use
for linenum, line in enumerate(myfile.readlines()): ...
Remember that true to Python's philosophy numbering will start at zero.
Is this any better than:
lines = myfile.readlines() for linenum in xrange(len(lines)): # Do stuff with lines[linenum] ...
Well, if you use lines[linenum] often in that code, it'll be more efficient to use enumerate (or bind lines[linenum] to a name, which is basically what enumerate is doing for you). Given the file test.py:
-------------------------------------------------- def elines(lines): for linenum, line in enumerate(lines): x = linenum y = line z = line
def xlines(lines): for linenum in xrange(len(lines)): x = linenum y = lines[linenum] z = lines[linenum]
--------------------------------------------------
Here's what I get with timeit:
[D:\Steve]$ python -m timeit -s"lines = range(10000); import test" "test.elines(lines)"
100 loops, best of 3: 2.85 msec per loop
[D:\Steve]$ python -m timeit -s"lines = range(10000); import test" "test.xlines(lines)"
100 loops, best of 3: 3.18 msec per loop
The other thing worth noting is that enumerate will work with any iterable, while your xrange technique won't. Try:
for linenum, line in enumerate(myfile):
...
and
for linenum in xrange(len(myfile)):
line = myfile[linenum]
...
and see what kind of cool errors you get with the xrange solution. :)
STeVe
Wow that is significant evidence. Thanks for doing that.
This is the first time I have posted to this list. I really like it for two reasons. 1) There are lots of people who are willing to help out and 2) there are so many ideas now I can pick which one I like best. I think I am leaning towards using enumerate.
Thanks, Jeremy
-- http://mail.python.org/mailman/listinfo/python-list
