This code extracts all the digits from the string `phone_number`...

This code extracts all the digits from the string phone_number and combines them into a new string. Here’s a detailed explanation:

1. filter(str.isdigit, phone_number):
   The filter() function applies the str.isdigit method on each character of the phone_number string.

   • str.isdigit checks if a character is a digit (0–9).
   • Only characters that are digits are included in the filtered result.

2. ''.join(...):
   The join() function takes the filtered digits and combines them into a single string, with no delimiter (since an empty string '' is specified).

Example:

If phone_number = "(123) 456-7890", the code extracts and returns:

'1234567890'

In summary, this code removes all non-digit characters from the string phone_number, leaving only the digits as a single concatenated string.