Changing value of different columns using a function in pandas

Question

i have a dataframe:

Now i want to replace 1 with 3, 2 with 7 ,and 3 with 10.

I write the code:

df['A'].replace(3, 10, inplace = True)
df['A'].replace(1, 3, inplace = True)
df['A'].replace(2, 7, inplace = True)

Works fine for me. I do have to replace 3 with 10 first , because if we change the 1 with 3 first, then the transformed 3 will again changed and finally replaced with 10.

Though i have to replace the same formattion for several columns, how come i use function?

I tried to write one but i failed, any guidance?

Josmoor98 · Accepted Answer · 2020-02-29 17:48:16Z

1

If you want to apply this to all columns, you can use

to_replace = {3:10, 1:3, 2:7}

df = df.replace(to_replace)

which outputs

    A   B   C
0   3   3   3
1   7   7   7
2   10  10  10

If you want to replace multiple, but not all, you could try

df = df.replace({'A' : to_replace, 'B': to_replace})

which would outputs.

    A   B   C
0   3   3   1
1   7   7   2
2   10  10  3

If you have many columns you would like to replace you could use

cols = ['A', 'B']

# Then either
df = df.replace({col : to_replace for col in cols})

# or
df[cols] = df[cols].apply(lambda x: x.replace(to_replace))

edited Feb 29, 2020 at 17:48

answered Feb 29, 2020 at 17:42

Josmoor98

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