What is NaN ? NaN, acronym for “Not a Number” is an exception which usually occurs in the cases when an expression results in a number that can’t be represented. For example square root of negative numbers.

What can I replace NaN with?

• For one column using pandas: df[‘DataFrame Column’] = df[‘DataFrame Column’].fillna(0)
• For one column using numpy: df[‘DataFrame Column’] = df[‘DataFrame Column’].replace(np.nan, 0)
• For the whole DataFrame using pandas: df.fillna(0)
• For the whole DataFrame using numpy: df.replace(np.nan, 0)

How do I know if I have NaN?

isNaN() method determines whether a value is NaN (Not-A-Number). This method returns true if the value is of the type Number, and equates to NaN. Otherwise it returns false. Number.