Cannot Save to CSV from Groupby - pandas

Question

Iam newbie in python. I have huge a dataframe with millions of rows and id. my data looks like this:
Time ID X Y
8:00 A 23 100
9:00 B 24 110
10:00 B 25 120
11:00 C 26 130
12:00 C 27 140
13:00 A 28 150
14:00 A 29 160
15:00 D 30 170
16:00 C 31 180
17:00 B 32 190
18:00 A 33 200
19:00 C 34 210
20:00 A 35 220
21:00 B 36 230
22:00 C 37 240
23:00 B 38 250
I sorted the data on id and time.
Time ID X Y
8:00 A 23 100
13:00 A 28 150
14:00 A 29 160
18:00 A 33 200
20:00 A 35 220
9:00 B 24 110
10:00 B 25 120
17:00 B 32 190
21:00 B 36 230
23:00 B 38 250
11:00 C 26 130
12:00 C 27 140
16:00 C 31 180
19:00 C 34 210
22:00 C 37 240
15:00 D 30 170
and I want to pick only "The first and the last" of the id and eliminate the rest. The result looked like this:
Time ID X Y
8:00 A 23 100
20:00 A 35 220
9:00 B 24 110
23:00 B 38 250
11:00 C 26 130
22:00 C 37 240
15:00 D 30 170
I used this code:
df = pd.read_csv("contoh.csv")
g = df.groupby('ID')
(pd.concat([g.head(1), g.tail(1)])
.drop_duplicates()
.sort_values('ID')
.reset_index(drop=True))
It works but I cannot save to csv
g.to_csv('result.csv')
I got an error message: Cannot access callable attribute 'to_csv' of 'DataFrameGroupBy' objects, try using the 'apply' method
any advice to me? thank you

Answer 1

When you are using the concat function, you are not applying it on the groupby object g. You need to reassign the concat function's output to another object.
df = pd.read_csv("contoh.csv")
g = df.groupby('ID')
g_1 = pd.concat([g.head(1),g.tail(1)]).drop_duplicates().sort_values('ID').reset_index(drop=True)
g_1.to_csv('result.csv')