Python: trying to check for a valid phone number

Question

I am trying to write a program that accepts a phone number in the format XXX-XXX-XXXX and translates any letters in the entry to their corresponding numbers.

Now I have this, and it will allow you to reenter the correct number if its not correct to start, but then it translates the original number entered. how do i fix this?

def main():
    phone_number= input('Please enter a phone number in the format XXX-XXX-XXXX: ')
    validNumber(phone_number)
    translateNumber(phone_number)

def validNumber(phone_number):
for i,c in enumerate(phone_number):
    if i in [3,7]:
        if c != '-':
            phone_number=input('Please enter a valid phone number: ')
        return phone_number
    elif not c.isalnum():
        phone_number=input('Please enter a valid phone number: ')
        return phone_number
return phone_number


def translateNumber(phone_number):
    s=""
    for char in phone_number:
        if char is '1':
            x1='1'
            s= s + x1
        elif char is '-':
            x2='-'
            s= s + x2
        elif char in 'ABCabc':
            x3='2'
            s= s + x3
        elif char in 'DEFdef':
            x4='3'
            s= s + x4
        elif char in 'GHIghi':
            x5='4'
            s= s + x5
        elif char in 'JKLjkl':
            x6='5'
            s= s + x6
        elif char in 'MNOmno':
            x7='6'
            s= s + x7
        elif char in 'PQRSpqrs':
            x8='7'
            s= s + x8
        elif char in 'TUVtuv':
            x9='8'
            s= s + x9
        elif char in 'WXYZwxyz':
            x10='9'
            s= s + x10
    print(s)

Answer 1

import re

def validNumber(phone_nuber):
    pattern = re.compile("^[\dA-Z]{3}-[\dA-Z]{3}-[\dA-Z]{4}$", re.IGNORECASE)
    return pattern.match(phone_nuber) is not None

Answer 2

If you don't want to use regular expressions: You can use isalnum to check if something is a number or letter. You can access the nth character in a string using mystr[n] so, you could try:

def validNumber(phone_number):
    if len(phone_number) != 12:
        return False
    for i in range(12):
        if i in [3,7]:
            if phone_number[i] != '-':
                return False
        elif not phone_number[i].isalnum():
            return False
    return True

To see what phone_number[i] is doing, try this:

for i in range(len(phone_number)):
    print i, phone_number[i]

Using enumerate:

def validNumber(phone_number):
    for i,c in enumerate(phone_number):
        if i in [3,7]:
            if c != '-':
                return False
        elif not c.isalnum():
            return False
    return True

---

Once you have it working, you should use it later (inside of main) like:

def main():
    phone_number = '' # an invalid number to initiate while loop
    while not validNumber(phone_number):
        phone_number = input('Please enter a phone number in the format XXX-XXX-XXXX: ')
    translated_number = translateNumber(phone_number)