在python中对值进行分组和除法

Question

What I want to make records that have the same "NROCUENTA", create a column where the result of the first "SALDO" divided by the number of records in that group

import pandas as pd
import csv, sys
try:
 file_encoding = 'utf8'      
 input_fd = open('DAT_210.del', encoding=file_encoding)

 df = pd.read_csv(input_fd, sep = ' ', quotechar='"', error_bad_lines=False)
 result=df.groupby('NROCUENTA').apply(
    lambda x: ................................
 )
except csv.Error as e:
        sys.exit('file {}, line {}: {}'.format("datahist.del", reader.line_num, e))

resutl2=result.to_csv('result001.csv',mode = 'w', index=False )

SALDO=FIRST(SALDO)/COUNT(NROCUENTA)

DATA

 "NROCUENTA" "SALDO" 
"210-1-388" 159.20 
"210-1-388" 159.20 

"210-1-1219" 0.93 

"210-1-11657" 0.06 
"210-1-11657" 0.06 
"210-1-11657" 0.06 

RESULT

"210-1-388" 79.6 
"210-1-388" 79.6 

"210-1-1219" 0.93 

"210-1-11657" 0.02 
"210-1-11657" 0.02
"210-1-11657" 0.02

TRIED

I was trying with the dfply library, but it throws errors at me and I decided to do it with pandas

Answer 1

IIUC, you need transform with count and divide it by SALDO columns. I assign result to column AVG_SALDO

df['AVG_SALDO'] = df['SALDO'] / df.groupby('NROCUENTA').SALDO.transform('count')

Out[1112]:
     NROCUENTA   SALDO  AVG_SALDO
0    210-1-388  159.20      79.60
1    210-1-388  159.20      79.60
2   210-1-1219    0.93       0.93
3  210-1-11657    0.06       0.02
4  210-1-11657    0.06       0.02
5  210-1-11657    0.06       0.02