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Check If Pandas Column is of Category Type

In this tutorial, we will look at how to check if a column in a Pandas dataframe is a category type column or not with the help of some examples.

How to check if a Pandas column is a category column or not?

You can compare the column’s dtype with “category” to check whether a column is a category type column or not in Pandas. The following is the syntax –

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# check if column is a category column
df["Col"].dtype == "category"

# alternatively, you can also use hasattr()
hasattr(df["Col"], "cat")

It returns True if the column is of category dtype.

Examples

Let’s look at some examples of using the above methods. First, we will create a sample dataframe that we will be using throughout this tutorial.

import pandas as pd

# create a dataframe
df = pd.DataFrame({
        "Name": ["Tim", "Sarah", "Hasan", "Jyoti", "Jack"],
        "Shirt Size": ["Small", "Medium", "Large", "Small", "Large"]
})
# change to category dtype
df["Shirt Size"] = df["Shirt Size"].astype("category")
# display the dataframe
print(df)

Output:


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    Name Shirt Size
0    Tim      Small
1  Sarah     Medium
2  Hasan      Large
3  Jyoti      Small
4   Jack      Large

We now have a dataframe containing the name and t-shirt size information of some students in a university. Note that in the above code we converted the “Shirt Size” column to category dtype using the Pandas astype() function.

Check if a column is a Pandas categorical column

Let’s now check whether the “Shirt Size” column is a category type column or not. We use the above syntax to compare the column’s dtype with “category”.

# check if pandas column is of category type
print(df["Shirt Size"].dtype == "category")

Output:

True

We get True as the output indicating that the column is of category dtype.

Check if a Pandas series contains categorical data using hasattr()

Alternatively, you can also use the Python hasattr() function to check if a Pandas series contains categorical data or not (which is the same as checking whether it’s a category type column or not).

# check if pandas column is of category type
print(hasattr(df["Shirt Size"], "cat"))

Output:

True

Here, we check whether the “Shirt Size” column in the above dataframe has a “cat” attribute. We get True as the output, indicating that the column has a “cat” attribute and thus is a category type column in Pandas.


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Author

  • Piyush Raj

    Piyush is a data professional passionate about using data to understand things better and make informed decisions. He has experience working as a Data Scientist in the consulting domain and holds an engineering degree from IIT Roorkee. His hobbies include watching cricket, reading, and working on side projects.

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