When you want to loop around Python operators,

Navigating relationships between the Pandas columns.
By drawing two columns, you want to explore which operation the target column comes from between which two columns.

# This code is pseudo code based on python. It will not run. 
For i, j in combinations (df.columns, r=2): #itertools' combinations 
    For operator in [+, -, *, /]: # Core line of problem
        val_tmp = operator(df[i], df[j])
        if RMSE( df.target - val_tmp ) <0.01:
            print(i, operator, j)

The purpose is simple, but I don't know how to handle the looping part of those operators.

I think there's a smart way to deal with Ifelse, instead of tinkering with it and making it dirty.