pandas,使用args作为数据帧行条目

Question

我有一个pandas数据帧'df',有两列'A'和'B',我有一个带有两个参数的函数

def myfunction(B, A):
    # do something here to get the result
    return result

我想使用'apply'函数逐行将它应用到df

df['C'] = df['B'].apply(myfunction, args=(df['A'],))

但我得到了错误

ValueError: The truth value of a Series is ambiguous. Use a.empty, a.bool(), a.item(), a.any() or a.all().

什么发生在这里,似乎需要df ['A']作为整个系列!不仅仅是该系列中的行条目.

Answer 1

我想你需要:

import pandas as pd
df = pd.DataFrame({'A':[1,2,3],
                   'B':[4,5,6]})

print (df)
   A  B
0  1  4
1  2  5
2  3  6

def myfunction(B, A):
    #some staff  
    result = B + A 
    # do something here to get the result
    return result

df['C'] = df.apply(lambda x: myfunction(x.B, x.A), axis=1)
print (df)
   A  B  C
0  1  4  5
1  2  5  7
2  3  6  9

要么:

def myfunction(x):

    result = x.B + x.A
    # do something here to get the result
    return result

df['C'] = df.apply(myfunction, axis=1)
print (df)
   A  B  C
0  1  4  5
1  2  5  7
2  3  6  9