How to count the frequency of values in a Pandas DataFrame

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How to count the frequency of values in a Pandas DataFrame

Author：JIYIK Last Updated：2025/05/02 Views：

Sometimes, when you use DataFrame, you may want to count the number of times a value occurs in a column, or in other words, calculate the frequency. There are mainly three methods used for this. Let's look at them one by one.

df.groupby().count()
Series.value_counts()
df.groupby().size()

In the following sections, we will use the same DataFrameas follows:

import pandas as pd

df = pd.DataFrame(
    {
        "A": ["jim", "jim", "jim", "jim", "sal", "tom", "tom", "sal", "sal"],
        "B": ["a", "b", "a", "b", "b", "b", "a", "a", "b"],
    }
)

`df.groupby().count()`method

This method is best if you want to count the frequency of a single column.

import pandas as pd

df = pd.DataFrame(
    {
        "A": ["jim", "jim", "jim", "jim", "sal", "tom", "tom", "sal", "sal"],
        "B": ["a", "b", "a", "b", "b", "b", "a", "a", "b"],
    }
)

freq = df.groupby(["A"]).count()
print(freq)

freq = df.groupby(["B"]).count()
print(freq)

Output:

     B
A     
jim  4
sal  3
tom  2
   A
B   
a  4
b  5

`Series.value_counts()`method

Since every DataFrameobject is Seriesa collection of objects, this method is best used with pandas.Seriesobjects.

Now use Series.values_counts()the function

import pandas as pd

df = pd.DataFrame(
    {
        "A": ["jim", "jim", "jim", "jim", "sal", "tom", "tom", "sal", "sal"],
        "B": ["a", "b", "a", "b", "b", "b", "a", "a", "b"],
    }
)

freq = df["A"].value_counts()
print(freq)

freq = df["B"].value_counts()
print(freq)

Output:

jim    4
sal    3
tom    2
Name: A, dtype: int64
b    5
a    4
Name: B, dtype: int64

`df.groupby().size()`method

The above two methods cannot be used to calculate the frequency of multiple columns, but we can use them on multiple columns at the same time df.groupby().size().

import pandas as pd

df = pd.DataFrame(
    {
        "A": ["jim", "jim", "jim", "jim", "sal", "tom", "tom", "sal", "sal"],
        "B": ["a", "b", "a", "b", "b", "b", "a", "a", "b"],
    }
)

freq = df.groupby(["A", "B"]).size()
print(freq)

Output:

A    B
jim  a    2
     b    2
sal  a    1
     b    2
tom  a    1
     b    1
dtype: int64

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