Using Boolean indexing to change value

Question

I have a dataset that looks like this:

VendorAccount   FiscalPeriod    LCC
729616,             1,          False
729616,             2,          False
0,                  2,          False
1,                  4,          False

I attempted to use this line:

df['LCC'][(df['VendorAccount'] == 729616) & df['FiscalPeriod'] >1] = True

to make it look like this:

VendorAccount   FiscalPeriod    LCC
729616,             1,          False
729616,             2,          True
0,                  2,          False
1,                  4,          False

The script runs but no changes are being made. Can anyone advise me on where I am going wrong?

Alex F · Accepted Answer · 2021-10-26 17:27:56Z

1

& operator has higher precedence than >, hence your original code is equivalent to this:

df['LCC'][((df['VendorAccount'] == 729616) & df['FiscalPeriod']) > 1] = True

To update the dataframe correctly you should use the following code instead:

df['LCC'][(df['VendorAccount'] == 729616) & (df['FiscalPeriod'] > 1)] = True

answered Oct 26, 2021 at 17:27

Alex F

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