python - 将列中的零替换为上一行中的字符串(Python/Pandas)

Question

我想用上一行同一列中的字符串替换 0。例如:Sheffield 下的 0 应为 Sheffield。我正在与 Pandas 一起工作。

file = file[['Branch', 'Type' ,'total']]
#replace NaN with 0 
file.fillna(0).tail(6)
Out[48]: 
     Branch                     Type  total

394   Sheffield  Sum of Resend to Branch      0
395           0   Number of PV Enquiries     83
396   Wakefield  Sum of Resend to Branch      0
397           0   Number of PV Enquiries     38
398        York  Sum of Resend to Branch      1
399           0   Number of PV Enquiries     59

I have tried:
a) #create a  series for that column and replace
branch = file.iloc[ :, 0]
branch.replace(0, branch(-1))
# why is this series not callable?

b)# I tried a loop in the dataframe
for item in file:
    if "Branch" == 0:
        replace(0, "Branch"[-1])
# I am unsure how to refer to the row above

Answer 1

将replace与方法ffill结合使用

file_df['Branch'].replace(to_replace='0', method='ffill', inplace=True)

>>> file_df
        Branch                     Type  total
394  Sheffield  Sum of Resend to Branch      0
395  Sheffield   Number of PV Enquiries     83
396  Wakefield  Sum of Resend to Branch      0
397  Wakefield   Number of PV Enquiries     38
398       York  Sum of Resend to Branch      1
399       York   Number of PV Enquiries     59

或者，由于您似乎已经将 NaN 替换为 0，因此您可以省略该步骤并仅使用 ffill。 即如果您的原始数据框如下所示:

>>> file_df
        Branch                     Type  total
394  Sheffield  Sum of Resend to Branch      0
395        NaN   Number of PV Enquiries     83
396  Wakefield  Sum of Resend to Branch      0
397        NaN   Number of PV Enquiries     38
398       York  Sum of Resend to Branch      1
399        NaN   Number of PV Enquiries     59

用途:

file_df['Branch'].ffill(inplace=True)

请注意，我将您的数据框称为 file_df 而不是 file ，以免屏蔽 python 内置