Filter and assignment || Filter and concat - not able to produce the desired result.

[ashvinmanoj]

This topic is from 1494

I am trying to replicate a pandas syntax but unable to succeed with Vaex.

(Datafarme['A'])[(Dataframe['A'] == '')] = (Datafarme['B'])[(Dataframe['A'] == '')]

I am trying to fill the empty rows on Column A with values from Column B when row values in column A is empty.
Expression on left and right produces a result when executed independently, but together the assignment is not working.

Same syntax in vaex gives an error "Expression" does not support item assignment

Alternative:
I tried splitting the dataframe into two, DF1 with Column A having empty values and DF2 with column A having non empty values. Then copy Column B into Column A on DF1. Then use DF1.concat(DF2), but this ended in error too

You have passed in an object for which we cannot determine a fingerprint

Both column A and B are string.
I am using Python 3.8.5 on windows with Vaex 4.3.0
Vaex was installed using pip install vaex inside my anaconda environment.

Is it possible to achieve the above goal through Vaex?

**NOTE **

The solution suggested in the issue 1494 will not produce the result what I am looking for. Join will only give the row count of my df1 (plus any duplicate rows) with additional columns from df2. But, I was referring to concatenation so I can get back the same no of rows as the original data frame.

[ashvinmanoj]

I found the solution myself,

DF['A]= DF.func.where(DF.A == '', DF.B, DF.A)