如何根据公共值将数据框中列的值添加到另一个数据框中？ 熊猫/蟒蛇

Question

Two dataframes:

df1:

Name
Sarah   
John   
J   
Fritz
Sarah
John

df2:

F_Name     gender   count
Sarah      F       1000
John       M       3500
Fritz      M       12540

Aim : if df1.name is in df2.F_Name then add column gender to df1. The expected answer is:

df1:

Name     gender
Sarah     F
John      M
J   
Fritz     M
Sarah     F
John      M

below code gives error: "Unalignable boolean Series provided as indexer"

df1['gender'] = df2[df1['Name'].isin(df2['Name'])]['gender'].values

Answer 1

尝试merge

df = df1.merge(df2.rename(columns = {'F_Name':'Name'}), on ='Name',how='left')

Answer 2

使用map ：

df1['gender'] = df1['Name'].map(df2.set_index('F_Name')['gender'])