How to count when a column has unique values in pandas?

Question

My file contains a column called 'Id';

eg:

Id  bill
---------
1   aaa
2   bbb
3   ccc
1   ddd
2   ee

I would like to return the count of Ids. Here it should be count(data['Id')) = 3 (not 5)

print(df.groupby('Id').count()) prints the whole file with rows count and column count. How can I make sure simple it prints how many unique Ids present in the column?

df["Id"].nunique().

Henry Yik
– Henry Yik

2019-10-10 04:25:10 +00:00
Commented Oct 10, 2019 at 4:25 — Henry Yik
– Henry Yik, Commented Oct 10, 2019 at 4:25
@HenryYik thanks this works

Ratha
– Ratha

2019-10-10 04:37:29 +00:00
Commented Oct 10, 2019 at 4:37 — Ratha
– Ratha, Commented Oct 10, 2019 at 4:37

jezrael · Accepted Answer · 2019-10-10 05:11:36Z

2

Use Series.nunique:

a = df["Id"].nunique()
print (a)
3

Or convert values to sets and get length:

a = len(set(df["Id"]))
print (a)
3

answered Oct 10, 2019 at 5:11

jezrael

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Comments

san · Accepted Answer · 2019-10-10 04:32:23Z

1

In your original attempt just use the length of the returned dataframe using len()

print(len(df.groupby('Id').count()))

answered Oct 10, 2019 at 4:32

san

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Comments

meTchaikovsky · Accepted Answer · 2019-10-10 04:29:54Z

1

You can also use collections.Counter, assume tmp is your dataframe

from collections import Counter

count = Counter(tmp['Id'])

answered Oct 10, 2019 at 4:29

meTchaikovsky

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