考虑顺序?
如果不考虑的话是用set() : uniqlines = set(open('/tmp/foo').readlines())
*Nix下sort <file name> | uniq

也有用dict的keys()的:

import collections

with open(infile, 'rb') as inf, open(outfile, 'wb') as outf:
outf.writelines(collections.OrderedDict.fromkeys(inf))


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要保持原顺序, 那就算一行一行读也能操作:
for ...
if line not in ... :
read_it



注: 我只是ST搬运工.