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pythonpandaslistdataframeexpand
FrankMank1
FrankMank1

Reputation: 73

How to expand a list in a pandas dataframe without repeating other column values

I was wondering how I would be able to expand out a list in a cell without repeating variables in other cells.

Dataframe Before

Dataframe After

The goal is to get it so that the list is expanded but the first column is not repeated. I know how to expand the list out but I would not like to have the first column values repeated if that is possible. Thank you for any help!!

Upvotes: 1

Views: 2020

Answers (1)

LTheriault
LTheriault

Reputation: 1230

In order to get what you're asking for, you still have to use explode() to get what you need. You just have to take it a step further and change the values of the first column. Please note that this will destroy the association between the elements of the list and the letter of the row they were first in. You would be creating a third value for the column (an empty string) that would be repeated for every record not beginning with 1.

If you want to eliminate the value from the rows you are talking about but still want to have those records associated with the value that their list was associated with, you can't. It's not logically possible for a value to both be in a given cell but also not be in that cell. So, I will show you the steps for eliminating the original association.

For this example, I named the columns since they are not provided.

data = [
    ["a",["1 hey","2 hi","3 hello"]],
    ["b",["1 what","2 how","3 say"]]
]
df = pd.DataFrame(data,columns=["first","second"])
df = df.explode("second")
df['first'] = df.apply(lambda x: x['first'] if x['second'][0] == '1' else '', axis=1)

Upvotes: 2

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