如何比较数据框中的两列并根据匹配字段更新列

Question

我有两个数据框，如下所示

|a|b|c|
|1|2| |
|4|5| |
|7|8| |

第二个数据帧是

|a_1|b_1|
|1  |5  |
|4  |2  |
|7  |8  |

我想比较两个公共列 (a,a_1) 并更新我的第一个数据框中的第 3 列。预期输出如下所示

    |a|b|c|
    |1|2|5|
    |4|5|2|
    |7|8|8|

是否有匹配公共列并填充第 3 列的代码？

Answer 1

import pandas as pd

d1={
    "a":(1,4,7),
    "b":(2,5,8),
    "c":(0,0,0)
}

d2={
    "a_1": (1, 4, 7),
    "b_1": (5, 2, 8)
}

df1=pd.DataFrame(d1)
df2=pd.DataFrame(d2)

# Iterate through each entry in a and compare it to a_1
for i in range(len(df1["a"])):
    for j in range(len(df2["a_1"])):
        if df1["a"][i] == df2["a_1"][j]:
            df1["c"][i] = df2["b_1"][j]

如何比较数据框中的两列并根据匹配字段更新列

how to compare two columns in dataframe and update a column based on matching fields

python

dataframe

pandas

data-science