CODEWITHSUNDEEP
pythonpandas
MRocklin
MRocklin

Reputation: 57271

Fastest way to count number of occurrences in Pandas

What is the fastest way to compute the number of occurrences of elements within a Pandas series?

My current fastest solution involves .groupby(columnname).size(). Is there anything faster within Pandas? E.g. I want something like the following:

In [42]: df = DataFrame(['a', 'b', 'a'])

In [43]: df.groupby(0).size()
Out[43]: 
0
a    2
b    1
dtype: int64

Upvotes: 1

Views: 974

Answers (1)

cwharland
cwharland

Reputation: 6703

The value_counts() function in pandas does this exactly.

Use that function on the column you want. i.e.

df['column_i_want'].value_counts()

Upvotes: 3

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