如何用python在csv中附加列

Question

我有一个类似4列的csv文件test.csv

A   |  B   |  C  | D
======================
aed | etge | 3r4 | pu9
frt | eide | 9h4 | sd2
jey | edlr | 8d2 | bu6

使用python，我希望将B列附加在A列下，将D列附加在C列下所以我有低于的

A    |  C 
===========
aed  | 3r4 
frt  | 9h4 
jey  | 8d2 
etge | pu9
eide | sd2
edlr | bu6

Answer 1

建议使用panda。

试试这样的东西：

import pandas as pd
dataFrame = pd.DataFrame({"A":["aed","etge","3r4"],
"B":["aed","etawge","3r4"],
"C":["aed","etgase","3r4"],
"D":["aed","etgqee","3r4"],})
AB = pd.concat([dataFrame["A"],dataFrame["B"]])
CD = pd.concat([dataFrame["C"],dataFrame["D"]])
final_dataFrame = pd.concat([AB,CD], axis=1)
final_dataFrame.columns=["A","C"]

我没有使用与您完全相同的数据，但这说明了如何做到这一点。您可以使用pandas.read_csv读取csv文件。

编辑：如果你想直接从文件中读取，你必须首先更改文件，使其没有"=====&"；，所以它应该是这样的：

A   |  B   |  C  | D
aed | etge | 3r4 | pu9
frt | eide | 9h4 | sd2
jey | edlr | 8d2 | bu6

一旦完成，就这样做：

# read the file. If test.csv is not in the same folder, then you have to give the complete file path.
dataFrame = pd.read_csv("test.csv", sep="|")
# remove unnecessary white spaces.
dataFrame = dataFrame.apply(lambda x: x.str.strip() if x.dtype == "object" else x)
# create a new column by combining column 0 and 1.
AB = pd.melt(dataFrame.iloc[:, [0, 1]])["value"]
# create a new column by combining column 2 and 3.
CD = pd.melt(dataFrame.iloc[:, [2, 3]])["value"]
# combine the previous two columns
final_dataFrame = pd.concat([AB, CD], axis=1)
# give them names "A" and "C"
final_dataFrame.columns = ["A", "C"]
print(final_dataFrame)

如果你不担心可读性，你可以将不同的步骤组合起来，如下所示：

dataFrame = pd.read_csv("file.csv", sep="|").apply(lambda x: x.str.strip() if x.dtype == "object" else x)
final_dataFrame = pd.concat([pd.melt(dataFrame.iloc[:, [0, 1]])["value"], pd.melt(dataFrame.iloc[:, [2, 3]])["value"]], axis=1)
final_dataFrame.columns = ["A", "C"]
print(final_dataFrame)

这给出了结果：

A    C
0   aed  3r4
1   frt  9h4
2   jey  8d2
3  etge  pu9
4  eide  sd2
5  edlr  bu6