How to make a calculated field in a DataFrame by condition?

Question

Python

For example, a calculated field The problem is that m can be equal to 0. It is necessary that when m = 0, then the value of the calculated field is equal to 0. How to do this?
df['new'] = df.n / df.m

Answer 1

df['new'] = df.n / df.m if df.m != 0 else 0

Answer 2

Describe a function that takes n and m and divides n by m. If m==0 returns 0.
And then just call this function with your arguments:
df['new'] = foo(df.n, df.m)