Is it possible to add to a string based on user input python

Question

I am currently working on a program that takes in user inputs, and depending on that users input the string should change. I was wondering if there was a way I could alter the string once the user input has been received. The following is a sample code.

title = input('Title: ')
subtitle = input('Subtitle: ')
chapter = input('Chapter: ')
subchapter = input('Subchapter: ')

title1 = '/title{}'.format(title)
subtitle1 = '/subtitle{}'.format(subtitle)
chapter1 = '/chapter{}'.format(chapter)
subchapter1 = '/subchapter{}'.format(subchapter)

output_txt = title1+subtitle1+chapter1+subchapter1
print(output_txt)

1. Input taken by user: Should be a number
2. The input would then be formatted to its perspective string
3. Based on the user input the string, output_txt, should be formatted accordingly

Scenario 1: User Input

Title: 4
Subtitle:
Chapter: 12
Subchapter: 1

output_txt should be

output_txt = '/title4/chapter12/subchapter1'

Scenario 2: User Input

Title: 9
Subtitle: 
Chapter: 2
Subchapter: 

output_txt should be

output_txt = '/title9/chapter2'

I have been using if elif but since there could be multiple combinations I do not think doing it that way is the most efficient.

Any help or tips in the right direction is greatly appreciated

Answer 1

Here's an approach that uses a regular expression for input validation and list comprehensions to gather the inputs and build the output string.

import re


def get_input( label: str = None ) -> int:
    entry = input(label + ': ')

    if re.match(r'^\d+$', entry) is None:
        return None

    if int(entry) <= 0:
        return None

    return int(entry)


tpl_labels = ('Title', 'Subtitle', 'Chapter', 'Subchapter')

lst_values = [get_input(x) for x in tpl_labels]

output_txt = '/'.join([f'{x.lower()}{y}' for x, y in zip(tpl_labels, lst_values) if y])

if not output_txt:
    print('No valid responses given.')
else:
    output_txt = '/' + output_txt
    print(output_txt)

The get_input() function expects each value entered by the user to be a positive integer. All other input is silently ignored (and None is returned).