如何比较两个 CSV 文件并获得差异？答案

【问题标题】：How to compare two CSV files and get the difference?如何比较两个 CSV 文件并获得差异？
【发布时间】：2021-02-16 07:58:37
【问题描述】：

我有两个 CSV 文件，

a1.csv

city,state,link
Aguila,Arizona,https://www.glendaleaz.com/planning/documents/AppendixAZONING.pdf
AkChin,Arizona,http://www.maricopa-az.gov/zoningcode/wp-content/uploads/2014/05/Zoning-Code-Rewrite-Public-Review-Draft-3-Tracked-Edits-lowres1.pdf
Aguila,Arizona,http://www.co.apache.az.us/planning-and-zoning-division/zoning-ordinances/

a2.csv

city,state,link
Aguila,Arizona,http://www.co.apache.az.us

我想有所作为。

这是我的尝试：

import pandas as pd

a = pd.read_csv('a1.csv')
b = pd.read_csv('a2.csv')

mask = a.isin(b.to_dict(orient='list'))
# Reverse the mask and remove null rows.
# Upside is that index of original rows that
# are now gone are preserved (see result).
c = a[~mask].dropna()
print c

预期输出：

city,state,link
Aguila,Arizona,https://www.glendaleaz.com/planning/documents/AppendixAZONING.pdf
AkChin,Arizona,http://www.maricopa-az.gov/zoningcode/wp-content/uploads/2014/05/Zoning-Code-Rewrite-Public-Review-Draft-3-Tracked-Edits-lowres1.pdf

但我收到一个错误：

Empty DataFrame
Columns: [city, state, link]
Index: []**

我想根据前两行检查，如果它们相同，则将其删除。

【问题讨论】：

标签： python pandas csv

【解决方案1】：

您可以使用pandas 读取两个文件，将它们连接起来并删除所有重复的行：

import pandas as pd
a = pd.read_csv('a1.csv')
b = pd.read_csv('a2.csv')
ab = pd.concat([a,b], axis=0)
ab.drop_duplicates(keep=False)

参考：https://pandas.pydata.org/pandas-docs/stable/generated/pandas.DataFrame.drop_duplicates.html

【讨论】：

【解决方案2】：

首先，连接 DataFrame，然后删除重复项，同时仍保留第一个。然后重置索引以保持一致。

import pandas as pd

a = pd.read_csv('a1.csv')
b = pd.read_csv('a2.csv')
c = pd.concat([a,b], axis=0)

c.drop_duplicates(keep='first', inplace=True) # Set keep to False if you don't want any
                                              # of the duplicates at all
c.reset_index(drop=True, inplace=True)
print(c)

【讨论】：