python pandas groupby unexpected empty column

Question

I want to aggregate some data to append to a dataframe. The following gives me the number of wins per name import pandas as pd

data = [[1,'tom', 10], [1,'nick', 15], [2,'juli', 14], [2,'peter', 20], [3,'juli', 3], [3,'peter', 13]] 

have = pd.DataFrame(data, columns = ['Round', 'Winner', 'Score']) 

WinCount= have.groupby(['Winner']).size().to_frame('WinCount')
WinCount

, but the output does not give me two columns, named Winner and WinCount. In stead, the first column has no name, and the column name then appears on the second line:

How can I get a dataframe without these two "blank" fields

Use `WinCount=have.groupby(['Winner']).size().reset_index(name='WinCount')` — jezrael, Sep 20 '19 at 08:31

score 2 · Accepted Answer · answered Sep 20 '19 at 08:18

2

Try this

WinCount=have.groupby(['Winner']).size().to_frame('WinCount').reset_index()

Output

    Winner  WinCount
0   juli    2
1   nick    1
2   peter   2
3   tom     1

answered Sep 20 '19 at 08:18

moys

7,747
2
11
42

I only want one row per name\winner, not to append to the original dataframe – Ullsokk Sep 20 '19 at 08:23
code updated, please check. Initially i thought you wanted the row appended to the original dataframe. – moys Sep 20 '19 at 08:24
excellent, reset_index seems to be my new best friend! – Ullsokk Sep 20 '19 at 08:26

python pandas groupby unexpected empty column

1 Answers1