How to define a variable amount of columns in python pandas apply

Question

I am trying to add columns to a python pandas df using the apply function. However the number of columns to be added depend on the output of the function used in the apply function.

example code:

number_of_columns_to_be_added = 2    
def add_columns(number_of_columns_to_be_added):
         df['n1'],df['n2'] = zip(*df['input'].apply(lambda x : do_something(x, number_of_columns_to_be_added)))

Any idea on how to define the ugly column part (df['n1'], ..., df['n696969']) before the = zip( ... part programatically?

Answer 1

I'm guessing that the output of zip is a tuple, therefore you could try this:

temp = zip(*df['input'].apply(lambda x : do_something(x, number_of_columns_to_be_added)))
for i, value in enumerate(temp, 1):
    key = 'n'+str(i)
    df[key] = value

temp will hold the all the entries and then you iterate over tempto assign the values to your dict with your specific keys. Hope this matches your original idea.