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df_train[catcols] = df_train[catcols].fillna("NANO")
df_test[catcols[:-2]] = df_test[catcols[:-2]].fillna("NANO")
David Erickson
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Derilxavier
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    All `NaN` values in the selected columns willbe replaced with `NANO`. Does this answer your question? [How to replace NaN values by Zeroes in a column of a Pandas Dataframe?](https://stackoverflow.com/questions/13295735/how-to-replace-nan-values-by-zeroes-in-a-column-of-a-pandas-dataframe) – David Erickson Aug 06 '20 at 06:47
  • yeah understood DavidErickson – Derilxavier Aug 06 '20 at 07:06

1 Answers1

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fillna is a method in pandas series and dataframe. It replaces NA/NAN values in a dataframe.

Syntax :

df.fillna(value=None, method=None, axis=None, inplace=False, limit=None, downcast=None, **kwargs)

In this case

df_train[catcols] = df_train[catcols].fillna("NANO")
df_test[catcols[:-2]] = df_test[catcols[:-2]].fillna("NANO")

'NANO' string is replaces where a NONE value is found in the dataframe.

For example:

if your dataframe df is :

Index   Name
1      Jacob
2      Andrew
3       NONE
4       NONE
5      Steve

df['Name'].fillna('Aagam')

Index   Name
1      Jacob
2      Andrew
3      Aagam
4      Aagam
5      Steve

to learn more visit Pandas.dataframe.fillna

Aagam Sheth
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