how to return None for empty array in python?

Question

I have a dataframe with two columns. Column one contains an integer, the second column a list with multiple items, which also can be empty. I want to return a list with tuples, in which the first part of the tuple is the integer from col1, and the second part of the tuple is the integer from col2, listing in total all possible outcomes. Input:

    col1    col2
0   909101  [1396920, 3094857]
1   21095887    [8383568]
2   8383568 [21095887]
3   2408689 []

desired output:

[(909101, 1396920),
(909101, 3094857),
 (21095887, 8383568),
 (8383568, 21095887),
 (2408689, None)]

So far, I have these, but it only outputs tuples for non empty inputs.

[(df[col1][i],df[col2][i][j]) 
            for i in range(len(df))
            for j in range(len(df[col2][i]))]

[(909101, 1396920),
(909101, 3094857),
 (21095887, 8383568),
 (8383568, 21095887)]

Have you tried doing this with normal for loops? This will make it easier for you to add a simple if statement to handle the special case. — mkrieger1
– mkrieger1, Commented Nov 17, 2021 at 12:49

user2390182 · Accepted Answer · 2021-11-17 12:50:01Z

1

One quick and dirty fix, turning the second loop into a normal for-each loop:

[(df[col1][i], x) 
            for i in range(len(df))
            for x in (df[col2][i] or [None])]

answered Nov 17, 2021 at 12:50

user2390182

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