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Python

Python Recursion

I'm trying to write a recursive function but got stuck. A really long explanation would help.

times is the number of times to repeat and data is the number or string to be repeated e.g replicate_recur(3, 5) should return [5,5,5].

Here is my attempt.

def replicate_recur(times, data):
    """This is a recursive function
    that returns an array containing repetitions of the data argument"""
    if not isinstance(times, int):
        raise ValueError('Invalid argument')
    elif not isinstance(data, (int, str)):
        raise ValueError('Invalid argument')
    elif times <= 0:
        return []
    else:
        arr = []
        if len(arr) == times:  # base case
            return arr  # no recursive call
        else:
            return [(str(data) + ',') * times]

1 Answer

Steven Parker
Steven Parker
229,017 Points

Remember that a recursive function will call itself, but with one or more arguments modified. For example, a function to add all numbers from 1 to a specific end value might look like this:

def add_numbers(val):
    if val > 1:
        return val + add_numbers(val - 1)
    return 1

You should find that your function will require much less code once you structure it to just do a part of the task, and use itself to do the rest.