Pandas GroupBy.apply method duplicates first group

Question

My first SO question: I am confused about this behavior of apply method of groupby in pandas (0.12.0-4), it appears to apply the function TWICE to the first row of a data fr

Answer 1

you can use for loop to avoid the groupby.apply duplicate first row,

log_sample.csv

guestid,keyword
1,null
2,null
2,null
3,null
3,null
3,null
4,null
4,null
4,null
4,null

my code snippit

df=pd.read_csv("log_sample.csv") 
grouped = df.groupby("guestid")

for guestid, df_group in grouped:
    print(list(df_group['guestid'])) 

df.head(100)

output

[1]
[2, 2]
[3, 3, 3]
[4, 4, 4, 4]