Question

Preliminaries

For this lab you will be working with regular expressions in Python. Various functions for working with regular expressions are available in the re module. Fortunately, Python makes it pretty easy to check if a string matches a particular pattern.

At the top of the file we must import the re module: import re

Then we can use the search() function to test whether a string matches a pattern. In the example below, the regular expression has been saved in a string called pattern for convenience:

phone = "123-456-7890"
pattern = r"ˆ\d{3}-\d{3}-\d{4}$"
if re.search(pattern, phone):

    print("The string matches the pattern.")
else:

    print("The string does not match the pattern.")

The r that precedes the pattern string is not a typo. Rather, the r indicates that the string is a “raw” string. In a raw string, as opposed to a “normal” string, any backslash character is interpreted as simply a backslash, as opposed to defining an escape sequence like \n or \t. Make sure you use raw strings in your Python code when defining regular expressions.

The ˆ and $ at the respective beginning and end of the regular expression indicate that the entire string must match the regular expression, and not just part of the string. Make sure you include these symbols in your regular expressions too!

You can play around with regular expressions on this web=based platform: regex101.com.Part I: Phone Number Checker

PART 1

Write a Python function phone number() that takes one parameter, which is a list of strings, each being a potential phone number. The function examines each string in the list and returns a list of indexes of those strings which meet the following description/requirement:

A valid string starts with (i) an optional open parenthesis, "("; followed by (ii) three digits (the first one being non-zero); then followed by (iii) an optional close parenthesis, ")" (the close parenthesis will only be present if there is a corresponding open parenthesis and vice versa); then followed by (iv) an optional hyphen, "-"; followed by (v) three more digits; followed by (vi) an optional hyphen,"-" again; and finally ends with (vii) four more digits.

Few valid examples of this format are: "(631)111-2211", "631111-2211", "631-111-2211"etc.
Fewinvalidexamplesare:"(631111-2211","631 111-2211","631)-111-2211"etc.

Note: A validly formatted string may not contain any spaces.Examples:

Function Arguments	Return Value
[’(091)-111-1234’, ’6311112222’, ’(631)-111-2222’, ’(631) 111-2222’]	[1, 2]
[’091-111-1234’, ’631 111 2222’, ’(631)1112222’, ’0911111234’]	[2]
[’631-1111-234’, ’631--111-2222’, ’(6311112222’, ’631)1111234’]	[]
[’(631)-8675309’, ’6311112222’, ’(631)111-2222’, ’(631)1111234’]

Answer 1

import re


def phonenumber(numbers):
    valid = []
    for i in range(0, len(numbers)):
        # If current number in list is valid
        # Append its index to valid list
        if validateNumber(numbers[i]):
            valid.append(i)

    # Return valid list of indexes
    return valid


def validateNumber(num):
    # ^ matches start of string
    # \( matches opening brace
    # \[1-9]{3} matches [1-9] 3 digits
    # \) matches closing brace
    # \d{3} matches 3 digits
    # -? matches -, 0 or 1 times
    # \d{4} matches 4 digits
    # $ matches end of string

    pattern1 = r"^[1-9]{3}-?\d{3}-?\d{4}$"
    pattern2 = r"^\([1-9]{3}\)-?\d{3}-?\d{4}$"

    # If number matches any pattern of the two, means its valid
    # return true
    if re.search(pattern1, num) or re.search(pattern2, num):
        return True
    else:
        return False


if __name__ == '__main__':
    print(phonenumber(['(091)-111-1234', '6311112222', '(631)-111-2222', '(631) 111-2222']))
    print(phonenumber(['091-111-1234', '631 111 2222', '(631)1112222', '0911111234']))
    print(phonenumber(['631-1111-234', '631--111-2222', '(6311112222', '631)1111234']))
    print(phonenumber(['(631)-8675309', '6311112222', '(631)111-2222', '(631)1111234']))

SCREENSHOT

OUTPUT