comparing columns

[arvin]

I want to compare two columns.
If the values in column A is present in column B then the values should copy in column C with any special symbol in front
and if the values in column A is not present in column B then only that values should copy in column C without any special symbol in front.

Help!

[paul18fr]

if you want to get some advices, you should be more precise, and even show an example.

[arvin]

[paul18fr]

Initially I was thinking in something more complecated (entire column concern), but here, it seems you're working row by row: so I do not see any difficulty using at least "if ... then ... else".

[snippsat]

Can do it like this.

import pandas as pd
import numpy as np

df = pd.DataFrame({
    'col1': [1, 2, 3, 4, 10],
    'col2': [1, 4, 6, 8, 10]
    })

df['result'] = np.where(df['col1'] == df['col2'],  '*' + df['col2'].astype(str), df['col1'])

print(df)

Output:
   col1  col2 result
0     1     1     *1
1     2     4      2
2     3     6      3
3     4     8      4
4    10    10    *10

so I do not see any difficulty using at least "if ... then ... else".

Pandas is very different beast🦄 and not like ordinary Python code,
so if use if/else or a for loop then are in most cases doing something wrong or very ineffective in Pandas.

[paul18fr]

@snippsat: Pandas nor speed were originaly in the scope (first post); if so, I would have proposed the vectored form suggesting np.equal and np.where for instance.

In any way I'm wondering if he/she is asking for advices or asking somebody to do the job for him/her