Python Pandas Dataframe change cell value in loop not reflecting immediately

Question

I have a dataframe df as follows:

Regiment FinalScore

nighthawks -1

dragoons -1

scouts -1

for index_p, row_p in df.iterrows():
  df.ix[index_p, 'finalScore'] += 1
  print(row_p['finalScore'])

print(df)

What I get is:

-1

Regiment FinalScore

nighthawks 0

dragoons 0

scouts 0

Why is it that while changing the value of 'FinalScore' in the loop I do not get the updated values printed? And why are the updated values only reflected after the loop?

thanks

Because the iterator makes a copy, which you are printing. It does not reflect changes to the dataframe at all — Mad Physicist
– Mad Physicist, Commented Feb 14, 2017 at 1:17

Louisiana Hasek · Accepted Answer · 2017-02-14 01:19:39Z

1

The dataframe iterator returns a copy of the row, so you don't see your changes to the underlying row.

Reference: pandas.DataFrame.iterrows

answered Feb 14, 2017 at 1:19

Louisiana Hasek

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