[英]Add values to one column of a pandas dataframe based on the values in another
[英]Pandas add column from one dataframe to another based on a join
假设我有2个数据帧。 我想基于列查找向数据帧2添加一列数据帧1。 如果连接不可能,我想在额外的列中有一个常量(所以我可以对其进行过滤)。
图形:
码:
import pandas as pd
import numpy as np
data = np.array([['','Col1','Col2'],
['Row1','2','TWO'],
['Row2','1','ONE']]
)
data2 = np.array([['','Col3','Col4'],
['Row1','1','T1'],
['Row2','2','T2'],
['Row3','3','T3']]
)
df = pd.DataFrame(data=data[1:,1:],
index=data[1:,0],
columns=data[0,1:])
df2 = pd.DataFrame(data=data2[1:,1:],
index=data2[1:,0],
columns=data2[0,1:])
result_df = df2 + join Col2 based on df2.Col3 = df.Col1. Add certain string constant if join fails.
print(df)
print(df2)
print(result_df)
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