Pandas - count repeated values

Asked Jul 25 '20 at 18:25

Active Jul 25 '20 at 18:46

Viewed 47 times

With this:

df = pd.DataFrame({'players.name': ['John', 'Will' ,'John', 'Jim', 'Tim', 'John', 'Will', 'Tim'],
                    'players.diff': [0,0, 0, 0, 0, 0, 0, 0]})

But 'players.name' values are repeated many times, and I need to count the number os times each unique name appears, adding a column 'count', with this value, ending up with:

  players.name  players.diff  counts
0         John             0       3
1         Will             0       2
2         John             0       0
3          Jim             0       1
4          Tim             0       2
5         John             0       0
6         Will             0       2
7          Tim             0       2

How do I do this?

edited Jul 25 '20 at 18:46

asked Jul 25 '20 at 18:25

8-Bit Borges

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Hi, 5k rep user, you should already know this :) but can you please add a [mcve] that demonstrates what you're trying to do please? – cs95 Jul 25 '20 at 18:28
have you tried `df['players.diff'].unique()` or `df['players.diff'].nunique()`? – Mark Moretto Jul 25 '20 at 18:28
@cs95 thanks for the link, 219,770k rep user. sorry for that. – 8-Bit Borges Jul 25 '20 at 18:30
@DeepSpace Hmm...I may have misinterpreted what OP is asking. I'll leave it up because I own my mistakes! – Mark Moretto Jul 25 '20 at 18:33
@cs95, please refer to edit. – 8-Bit Borges Jul 25 '20 at 18:47
@MarkMoretto hope it's clearer now – 8-Bit Borges Jul 25 '20 at 18:51
1

For sure. I thought your post got deleted or something? Anyway, try: `counts_df = df.groupby("players.name").size().to_frame('counts').reset_index()` then `df = df.merge(counts_df, how='left', on="players.name")`. – Mark Moretto Jul 25 '20 at 19:02
yep, go ahead, thanks – 8-Bit Borges Jul 25 '20 at 19:03
@8-BitBorges Actually, I just edited that prev. comment. I used `groupby()` then `merge()`, which might work for you. If not, on merge you can set the 'how' parameter to 'outer' or 'left' to capture all values. I think default is 'inner'. – Mark Moretto Jul 25 '20 at 19:05
Why does `John` show a count of zero when it appears three times? – Dour High Arch Jul 26 '20 at 00:00

Pandas - count repeated values

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