使用Python合并两个CSV文件

Question

好的,我已经在Stack Overflow上阅读了几个主题.我认为这对我来说相当容易,但我发现我仍然没有很好地掌握Python.我尝试了如何将2个csv文件与公共列值组合在一起的示例,但两个文件都有不同的行数,这很有帮助,但我仍然没有我希望实现的结果.

基本上我有2个csv文件,共同的第一列.我想合并2. ie

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

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,但我想要的)

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(我实际获得的输出)

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])

任何帮助是极大的赞赏.

Answer 1

当我使用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:

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,我们读入csv文件:

>>> 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

我们看到有一个额外的数据列(注意fileb.csv- title,mar,apr,may,jun,- 的第一行- 在末尾有一个额外的逗号).我们可以很容易地摆脱它:

>>> 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,我们可以合并a,并b在标题栏:

>>> 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

Answer 2

您需要将文件中的所有额外行存储在字典中，而不仅仅是其中之一：

dict1 = {row[0]: row[1:] for row in r}
...
dict2 = {row[0]: row[1:] for row in r}

然后，由于字典中的值是列表，因此您只需将列表连接在一起：

w.writerows([[key] + dict1.get(key, []) + dict2.get(key, []) for key in keys])