Pandas update values of multiple rows of a column based on values of another column

Question

I have a dataframe like:

 column1  column2
   a        32
   b       175
   b       165
   a        80

and I want to update the value (multiplied by 10) of every row of column2 whose value in column1 == 'a'. The result is expected to be like:

 column1  column2
   a       320
   b       175
   b       165
   a       800

Tranbi · Accepted Answer · 2022-04-16 15:11:47Z

2

Very short with loc:

df.loc[df['column1']=='a', 'column2'] *= 10

You get:

  column1  column2
0       a      320
1       b      175
2       b      165
3       a      800

answered Apr 16, 2022 at 15:11

Tranbi

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Comments

Ynjxsjmh · Accepted Answer · 2022-04-16 15:16:47Z

1

Try np.where

df['column2'] = np.where(df['column1'].eq('a'), df['column2'].mul(10), df['column2'])

Or df.mask

df['column2'] = df['column2'].mask(df['column1'].eq('a'), df['column2'].mul(10))

  column1  column2
0       a      320
1       b      175
2       b      165
3       a      800

answered Apr 16, 2022 at 15:16

Ynjxsjmh

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