python - 如何从熊猫中的联合数据框左侧清除重复条目？

Question

为了在 pandas 中可视化和导出宽的左关节数据框，我想从左侧删除重复的条目。

我这是什么意思？

import pandas as pd

cities = pd.DataFrame().append([
    {"Name": "Peter", "City": "Boston"},
    {"Name": "Paul", "City": "Houston"}
    ], ignore_index=True)
emails = pd.DataFrame().append(    [
        {"Name": "Peter", "Email": "[e-mail]"},
        {"Name": "Peter", "Email": "[e-mail]"},
        {"Name": "Paul", "Email": "[e-mail]"},
    ], ignore_index=True)

print(cities.merge(emails))

这打印

    Name     City                 Email
0  Peter   Boston     [e-mail]
1  Peter   Boston  [e-mail]
2   Paul  Houston      [e-mail]

我想打印的是

    Name     City                 Email
0  Peter   Boston     [e-mail]
1                  [e-mail]
2   Paul  Houston      [e-mail]

我怎样才能实现这一点，理想情况下是在连接期间，这样我就不必跟踪哪些列来自前左侧和右侧？

标签： pythonpandasdataframejoin

Answer 1

按所有列使用Series.duplicated，然后设置''为DataFrame.mask：

df = cities.merge(emails)

df1 = df.mask(df.apply(pd.Series.duplicated), '')
print (df1)
    Name     City                 Email
0  Peter   Boston     [e-mail]
1                  [e-mail]
2   Paul  Houston      [e-mail]