Write a function called isphonenumber () to recognize a pattern 415-555-4242

Write a function called isphonenumber () to recognize a pattern 415-555-4242 without using regular expression and also write the code to recognize the same pattern using regular expression

Program:-

import re
def isphonenumber(numStr):
    if len(numStr) != 12:
        return False
    for i in range(len(numStr)):
        if i==3 or i==7:
            if numStr[i] != "-":
                return False
        else:
            if numStr[i].isdigit() == False:
                return False
    return True
def chkphonenumber(numStr):
    ph_no_pattern = re.compile(r'^\d{3}-\d{3}-\d{4}$')
    if ph_no_pattern.match(numStr):
        return True
    else:
        return False
ph_num = input("Enter a phone number : ")
print("Without using Regular Expression")
if isphonenumber(ph_num):
    print("Valid phone number")
else:
    print("Invalid phone number")
print("Using Regular Expression")
if chkphonenumber(ph_num):
    print("Valid phone number")
else:
    print("Invalid phone number")

Output:-

Enter a phone number : 444-654-5656
Without using Regular Expression
Valid phone number
Using Regular Expression
Valid phone number

Enter a phone number : 45A4-444-878
Without using Regular Expression
Invalid phone number
Using Regular Expression
Invalid phone number