How to test for nan in Pandas

In Pandas, you can use the isna() method to check for NaN (Not a Number) values in a DataFrame or Series. Here’s an example:

import pandas as pd
import numpy as np

# create a sample DataFrame with NaN values
df = pd.DataFrame({'A': [1, 2, np.nan], 'B': [4, np.nan, 6], 'C': [7, 8, 9]})

# check for NaN values in the DataFrame
print(df.isna())

# check for NaN values in a specific column
print(df['A'].isna())

The isna() method returns a boolean DataFrame or Series indicating which values are NaN. If a value is NaN, the corresponding element in the output will be True, otherwise it will be False.

Alternatively, you can use the isnull() method, which is equivalent to isna().