更新日期:2016

如果您乐意使用有用的 more_itertools 外部库:

If you are happy to use the helpful more_itertools external library:

from more_itertools import unique_everseen
with open('1.csv','r') as f, open('2.csv','w') as out_file:
    out_file.writelines(unique_everseen(f))

@IcyFlame解决方案的更有效版本

A more efficient version of @IcyFlame's solution

with open('1.csv','r') as in_file, open('2.csv','w') as out_file:
    seen = set() # set for fast O(1) amortized lookup
    for line in in_file:
        if line in seen: continue # skip duplicate

        seen.add(line)
        out_file.write(line)

要就地编辑同一文件，您可以使用此

To edit the same file in-place you could use this

import fileinput
seen = set() # set for fast O(1) amortized lookup
for line in fileinput.FileInput('1.csv', inplace=1):
    if line in seen: continue # skip duplicate

    seen.add(line)
    print line, # standard output is now redirected to the file