When I am looping over a file using the construct below, I also want the current line number.
with codecs.open(filename, 'rb', 'utf8' ) as f: retval = [] for line in f: process(line) Does something akin to this exist ?
for line, lineno in f: 
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2 Answers
for lineno, line in enumerate(f, start=1): If you are stuck on a version of Python that doesn't allow you to set the starting number for enumerate (this feature was added in Python 2.6), and you want to use this feature, the best solution is probably to provide an implementation that does, rather than adjusting the index returned by the built-in function. Here is such an implementation.
def enumerate(iterable, start=0): for item in iterable: yield start, item start += 1 
Comments
If you are using Python2.6+, kindall's answer covers it
Python2.5 and earlier don't support the second argument to enumertate, so you need to use something like this
for i, line in enumerate(f): lineno = i+1 or
for lineno, line in ((i+1,j) for i,j in enumerate(f)): Unless you are ok with the first line being number 0
2 Comments
Karl Knechtel
Are people still using 2.5 or earlier except for legacy support reasons?
John La Rooy
@Karl, I answered a question for someone using 2.4 earlier today