Python Pandas - Multiple assignment

Question

Is there an efficient way to make the following assignment without using for loops?

for i in range(0,len(df3)):
    if df3.loc[i,'field'] == "a":
        df3.loc[i,'field'] = "111"
    elif df3.loc[i, 'field'] == "b":
        df3.loc[i, 'field'] = "222"
    elif df3.loc[i, 'field'] == "c":
        df3.loc[i, 'field'] = "333"
    else:
        df3.loc[i,'field'] = "444"

why are you changing field in the last three elif, but a in the first? A typo? — Anand S Kumar
– Anand S Kumar, Commented Sep 30, 2015 at 16:09
For starters if you just did this df3.loc[df['field']=='a','field'] = '111' and so on you wouldn't need to iterate at all just call loc like above 4 times — EdChum
– EdChum, Commented Sep 30, 2015 at 16:12
It would be helpful if you provide the example of the data frame you start with and the data frame that you want to end with — lanenok
– lanenok, Commented Sep 30, 2015 at 17:09
Anand, thank you for pointing out the typo, i have modified my post. — Krisjay
– Krisjay, Commented Sep 30, 2015 at 17:23

rocconnick · Accepted Answer · 2015-09-30 23:02:46Z

1

You can simply do:

 df3.loc[df.field == 'a', 'field'] = '111'

and so on...

answered Sep 30, 2015 at 23:02

rocconnick

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Prune · Accepted Answer · 2015-09-30 16:16:06Z

0

You can shorten the code, but you still need a loop to hop through the df3 structure and hit all your "field" fields.

xlate = {'a':'111', 'b':'222', 'c':'333'}
for i in range(len(df3)):
    df3.loc[i, 'field'] = xlate.get(df3.loc[i, 'field'], '444')

answered Sep 30, 2015 at 16:16

Prune

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