如何从 csv 文件中删除重复项

我从 Hotmail 下载了一个 CSV 文件，但其中有很多重复项。这些副本是完整的副本，我不知道为什么我的手机创建了它们。

我想摆脱重复项。

技术规格:

Windows XP SP 3
Python 2.7
CSV file with 400 contacts
  

更新：2016

如果您乐意使用有用的more_itertools外部库：

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 解决方案的更高效版本

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，您可以使用它（旧的 Python 2 代码）

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