Replace None with NaN in pandas dataframe

You can use DataFrame.fillna or Series.fillna which will replace the Python object None, not the string 'None'.

import pandas as pd
import numpy as np

For dataframe:

df = df.fillna(value=np.nan)

For column or series:

df.mycol.fillna(value=np.nan, inplace=True)

Here's another option:

df.replace(to_replace=[None], value=np.nan, inplace=True)

The following line replaces None with NaN:

df['column'].replace('None', np.nan, inplace=True)

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