Python DataFrame：基于另一列的出现次数

Question

I have a Python Data Frame of teams and a place that they have achieved (1, 2 or 3)

Team	place
A	1
A	1
A	1
A	2
A	3
A	1
A	1
B	2
B	2

I want to manipulate the df to look like this below. So it is a count of how often a team has achieved each place.

Team	1	2	3
A	5	1	1
B	0	2	0

Answer 1

You can get the value counts for each group and then unstack the index. The rest is twiddling to get your exact output.

(df.groupby('Team')['place']
   .value_counts()
   .unstack(fill_value=0)
   .reset_index()
   .rename_axis(None, axis=1)
) 

Answer 2

You could use pandas.crosstab :

pd.crosstab(df['Team'], df['place'])

or a simple groupby + size and unstack :

(df.groupby(['Team', 'place']).size()
   .unstack('place', fill_value=0)
)

output:

place  1  2  3
Team          
A      5  1  1
B      0  2  0

all as columns

(pd.crosstab(df['Team'], df['place'])
   .rename_axis(columns=None)
   .reset_index()
)

output:

  Team  1  2  3
0   A   5  1  1
1   B   0  2  0