How can I say that if I want to return an operation on a list, but it stays the same when it comes out null?

I have a list-of-list of word groups in Turkish. I want to apply stemming and I found turkishnlp package. Although it has some shortcomings, it often returns the right word. However, when I apply this to the list, I don’t want the structure of my list to change and I want the words that he doesn’t know to stay the same.

For example, I have this list:
mylist = [[‘yolda’,’gelirken’,’kopek’, ‘gördüm’],[‘cok’, ‘tatlıydı’]]

And I wrote this function:

from trnlp import TrnlpWord
def tr_stemming(x):
    obj = TrnlpWord()
    obj.setword(x) if isinstance(x, str) else type(x)(map(tr_stemming, x))
    return obj.get_stem if isinstance(x, str) else type(x)(map(tr_stemming, x))

This function returns this list:

tr_stemming(mylist)

[[‘yol’, ‘gelir’, ”, ‘gör’], [”, ‘tatlı’]]

However, I want to get this as the output:
[[‘yol’, ‘gelir’, ‘kopek’, ‘gör’], [‘cok’, ‘tatlı’]]

How can I update my function?
Thank you for your helps!

>Solution :

IIUC, you could modify you could use:

def tr_stemming(x):
    if isinstance(x, str):
        obj = TrnlpWord()
        obj.setword(x)
        stem = obj.get_stem
        return stem if stem else x
    elif isinstance(x, list):
        return [tr_stemming(e) for e in x]
    
out = tr_stemming(mylist)

output:

[['yol', 'gelir', 'kopek', 'gör'], ['cok', 'tatlı']]