python - 使用 Python 合并两个 CSV 文件

Question

好的，我已经阅读了 Stack Overflow 上的几个主题。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。我尝试了位于 How to combine 2 csv files with common column value, but both files have different number of lines 的示例，这很有帮助，但我仍然没有得到我希望达到的结果。

基本上我有 2 个 csv 文件，它们有一个共同的第一列。我想合并2。即

filea.csv

title,stage,jan,febdarn,3.001,0.421,0.532ok,2.829,1.036,0.751three,1.115,1.146,2.921

fileb.csv

title,mar,apr,may,jun,darn,0.631,1.321,0.951,1.751ok,1.001,0.247,2.456,0.3216three,0.285,1.283,0.924,956

output.csv (not the one I am getting but what I want)

title,stage,jan,feb,mar,apr,may,jundarn,3.001,0.421,0.532,0.631,1.321,0.951,1.751ok,2.829,1.036,0.751,1.001,0.247,2.456,0.3216three,1.115,1.146,2.921,0.285,1.283,0.924,956

output.csv (the output that I actually got)

title,feb,mayok,0.751,2.456three,2.921,0.924darn,0.532,0.951

The code I was trying:

'''
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])

非常感谢任何帮助。

Answer 1

当我处理 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:

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)

---

下面是一些解释。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(注意第一行 fileb.csv -- title,mar,apr,may,jun, --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

现在我们可以在标题列合并a和b:

>>> 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)

制作:

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