使用Python合并两个CSV文件 [英] Merging two CSV files using Python
问题描述
好的，我已经在Stack Overflow上阅读了几个线程.我以为这对我来说很容易，但是我发现我仍然不太了解Python.我尝试了位于
OK I have read several threads here on Stack Overflow. I thought this would be fairly easy for me to do but I find that I still do not have a very good grasp of Python. I tried the example located at How to combine 2 csv files with common column value, but both files have different number of lines and that was helpful but I still do not have the results that I was hoping to achieve.
基本上，我有2个具有相同第一列的csv文件.我想合并2.即.
Essentially I have 2 csv files with a common first column. I would like to merge the 2. i.e.
filea.csv
filea.csv
title,stage,jan,feb
darn,3.001,0.421,0.532
ok,2.829,1.036,0.751
three,1.115,1.146,2.921
fileb.csv
fileb.csv
title,mar,apr,may,jun,
darn,0.631,1.321,0.951,1.751
ok,1.001,0.247,2.456,0.3216
three,0.285,1.283,0.924,956
output.csv(不是我得到的，而是我想要的)
output.csv (not the one I am getting but what I want)
title,stage,jan,feb,mar,apr,may,jun
darn,3.001,0.421,0.532,0.631,1.321,0.951,1.751
ok,2.829,1.036,0.751,1.001,0.247,2.456,0.3216
three,1.115,1.146,2.921,0.285,1.283,0.924,956
output.csv(我实际得到的输出)
output.csv (the output that I actually got)
title,feb,may
ok,0.751,2.456
three,2.921,0.924
darn,0.532,0.951
我正在尝试的代码:
'''
testing merging of 2 csv files
'''
import csv
import array
import os
with open('Z:\\Desktop\\test\\filea.csv') as f:
r = csv.reader(f, delimiter=',')
dict1 = {row[0]: row[3] for row in r}
with open('Z:\\Desktop\\test\\fileb.csv') as f:
r = csv.reader(f, delimiter=',')
#dict2 = {row[0]: row[3] for row in r}
dict2 = {row[0:3] for row in r}
print str(dict1)
print str(dict2)
keys = set(dict1.keys() + dict2.keys())
with open('Z:\\Desktop\\test\\output.csv', 'wb') as f:
w = csv.writer(f, delimiter=',')
w.writerows([[key, dict1.get(key, "''"), dict2.get(key, "''")] for key in keys])
非常感谢您的帮助.
推荐答案
在处理csv文件时，我经常使用 pandas 库.它使这样的事情变得非常容易.例如:
When I'm working with csv files, I often use the pandas library. It makes things like this very easy. For example:
import pandas as pd
a = pd.read_csv("filea.csv")
b = pd.read_csv("fileb.csv")
b = b.dropna(axis=1)
merged = a.merge(b, on='title')
merged.to_csv("output.csv", index=False)
一些解释如下.首先，我们读取csv文件:
Some explanation follows. First, we read in the csv files:
>>> a = pd.read_csv("filea.csv")
>>> b = pd.read_csv("fileb.csv")
>>> a
title stage jan feb
0 darn 3.001 0.421 0.532
1 ok 2.829 1.036 0.751
2 three 1.115 1.146 2.921
>>> b
title mar apr may jun Unnamed: 5
0 darn 0.631 1.321 0.951 1.7510 NaN
1 ok 1.001 0.247 2.456 0.3216 NaN
2 three 0.285 1.283 0.924 956.0000 NaN
，我们看到有一列额外的数据(请注意，fileb.csv的第一行-title,mar,apr,may,jun,的末尾有一个逗号).我们可以很容易地摆脱它:
and we see there's an extra column of data (note that the first line of fileb.csv -- title,mar,apr,may,jun, -- has an extra comma at the end). We can get rid of that easily enough:
>>> b = b.dropna(axis=1)
>>> b
title mar apr may jun
0 darn 0.631 1.321 0.951 1.7510
1 ok 1.001 0.247 2.456 0.3216
2 three 0.285 1.283 0.924 956.0000
现在，我们可以在标题列上合并a和b:
Now we can merge a and b on the title column:
>>> merged = a.merge(b, on='title')
>>> merged
title stage jan feb mar apr may jun
0 darn 3.001 0.421 0.532 0.631 1.321 0.951 1.7510
1 ok 2.829 1.036 0.751 1.001 0.247 2.456 0.3216
2 three 1.115 1.146 2.921 0.285 1.283 0.924 956.0000
最后写出来:
>>> merged.to_csv("output.csv", index=False)
生产:
title,stage,jan,feb,mar,apr,may,jun
darn,3.001,0.421,0.532,0.631,1.321,0.951,1.751
ok,2.829,1.036,0.751,1.001,0.247,2.456,0.3216
three,1.115,1.146,2.921,0.285,1.283,0.924,956.0
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