How to replace nan value with a date in a column?

Question

Sorry for the beginner-friendly question, but this code does not work for me and I can't find out why. It runs without errors, but it does not fill the values.

data['date'] = data['date'].replace(np.nan, '22.02.2021')

I tried using "fillna" function like this:

data['date'].fillna('22.02.2021', inplace=True)

but it gives error and says that fill value must be in categories.

Answer 1

Normally you can use pandas pd.to_datetime()

https://datatofish.com/replace-nan-values-with-zeros/ :

single column:

df['DataFrame Column'] = df['DataFrame Column'].fillna(value=pd.to_datetime('2/22/2021'), inplace=True)

entire dataframe:

df.fillna(value=pd.to_datetime('2/22/2021'), inplace=True)

However because of your comment that error ' Value error: fill value must be in categories ' is thrown anyway you have to change the dtype of column date in your dataframe from category to ie datetime64 see How do I convert strings in a Pandas data frame to a 'date' data type? and Change column type in pandas

When casting the datetime string ( 22.02.2021 ) using astype() you can skip using pd.datetime()