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AlexisHerrera
AlexisHerrera

Reputation: 23

"ValueError: Merge keys contain null values on right side" using pd.merge_asof

I'm trying to merge two dataframes using pd.merge_asof. There is a 'Date2' in df2 related to 'Date1' in df1. However, there are some rows where there is no 'Date2'.

I tried the below code to merge both dataframes, but I'm getting the following error: ValueError: Merge keys contain null values on right side

df3 = pd.merge_asof(df1.sort_values('Date1', ascending=True), 
                              df2.sort_values("Date2",ascending=True),
                               left_on='Date1', 
                               right_on='Date2', 
                               by=['Country','City','Location'], 
                               direction='forward')

Could anyone please help me to figure out how to handle the null values on Date2.

Upvotes: 2

Views: 4514

Answers (1)

davidbilla
davidbilla

Reputation: 2222

You can use .dropna() to remove the rows that have NaN values. Or use .fillna() to fill those rows with a default value .fillna(0) or use .fillna(method='ffill') to fill with the values from previous rows.

Upvotes: 2

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