copy dataframe lines and replace on the same dataframe

Question

I have a dataframe in which I have 2 records that are with few values, I wanted to replace those records with others with more values, make a copy. Does anyone know how to do this on pandas or vaex?

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wanted to replace the values ​​148 for example with the values ​​140 Someone help?

edit: my dataframe is this

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I would like to replace all values of day_of_week = 148 with values of day_of_week = 140 because (day_of_week = 148) has 1000 records and (day_of_week = 140) has 200000 records

I want to copy all lines day_of_year == 140 and replace for all lines that are day_of_year == 148

Answer 1

If I understand you correctly, this should be straightforward in vaex:

df['new_col'] = df.func.where(df.day_of_week==148, 140, df.day_of_week)

In vaex the new column will be virtual, ie not take any memory. So it does not matter if you overwrite your existing one, or keep a separate one with the mapping (maybe better to keep a separate one, in case you need to debug your process later on).

I think something similar can be done with pandas, using numpy.where as it was already commented before me.