What would be the pandas equivalent for the for-loop below?

Question

I have a function called unit_unify() that I want to apply to every column of the dataframe. I have been trying to devise the pandas equivalent using apply/apply map, but have not been successul.

Here is the for loop

for i in df.columns:
    df[i] = unit_unify(df[i], unit_dict)

Here is the attempt at the pandas equivalent of the for loop

df = df.apply(lambda col: unit_unify(df[col], unit_dict))

Answer 1

You may check the performance for the for loop and apply:link

[df[i] = unit_unify(df[i], unit_dict) for i in df.columns]