[ASSIGNMENT] string to number

Question

nearly all languages provide a conversion from string to number.
Do it yourself without the standard conversion.
input: string
output: number

please use error handling
have fun

Answer 1

https://code.sololearn.com/cESrAKvijVkr/?ref=app

Answer 2

inverse of this challenge
https://www.sololearn.com/learn/4603/?ref=app

Answer 3

https://code.sololearn.com/csB6aPeAZQZW/?ref=app