How to groupby based on two columns in pandas?

You need groupby with parameter as_index=False for return DataFrame and aggregating mean:
df = df.groupby([‘id’,’product’], as_index=False)[‘quantity’].sum()
print (df)
id product quantity
0 1 A 5
1 1 B 2
2 2 A 1
3 2 B 1
4 3 B 3

Or add reset_index:
df = df.groupby([‘id’,’product’])[‘quantity’].sum().reset_index()
print (df)
id product quantity
0 1 A 5
1 1 B 2
2 2 A 1
3 2 B 1
4 3 B 3

You can use pivot_table with aggfunc=’sum’
df.pivot_table(‘quantity’, [‘id’, ‘product’], aggfunc=’sum’).reset_index()

id product quantity
0 1 A 5
1 1 B 2
2 2 A 1
3 2 B 1
4 3 B 3