Soundex algorithm in Python (homework help request)

Question

The US census bureau uses a special encoding called “soundex” to locate information about a person. The soundex is an encoding of surnames (last names) based on the way a su

Answer 1

surname = input("Enter surname of the author: ") #asks user to input the author's surname

while surname != "": #initiates a while loop thats loops on as long as the input is not equal to an empty line

    str_ini = surname[0] #denotes the initial letter of the surname string
    mod_str1 = surname[1:] #denotes modified string excluding the first letter of the surname

    import re #importing re module to access the sub function
    mod_str2 = re.sub(r'[aeiouyhwAEIOUYHW]', '', mod_str1) #eliminating any instances of the given letters


    mod_str21 = re.sub(r'[bfpvBFPV]', '1', mod_str2)
    mod_str22 = re.sub(r'[cgjkqsxzCGJKQSXZ]', '2', mod_str21)
    mod_str23 = re.sub(r'[dtDT]', '3', mod_str22)
    mod_str24 = re.sub(r'[lL]', '4', mod_str23)
    mod_str25 = re.sub(r'[mnMN]', '5', mod_str24)
    mod_str26 = re.sub(r'[rR]', '6', mod_str25)
                #substituting given letters with specific numbers as required by the soundex algorithm

    mod_str3 = str_ini.upper()+mod_str26 #appending the surname initial with the remaining modified trunk

    import itertools #importing itertools module to access the groupby function
    mod_str4 = ''.join(char for char, rep in itertools.groupby(mod_str3))
                #grouping each character of the string into individual characters
                #removing sequences of identical numbers with a single number
                #joining the individually grouped characters into a string

    mod_str5 = (mod_str4[:4]) #setting character limit of the modified string upto the fourth place

    if len (mod_str5) == 1:
        print (mod_str5 + "000\n")
    elif len (mod_str5) == 2:
        print (mod_str5 + "00\n")
    elif len (mod_str5) == 3:
        print (mod_str5 + "0\n")
    else:
        print (mod_str5 + "\n")
                #using if, elif and else arguments for padding with trailing zeros

    print ("Press enter to exit") #specification for the interactor, to press enter (i.e., equivalent to a new line for breaking the while loop) when he wants to exit the program
    surname = input("Enter surname of the author: ") #asking next input from the user if he wants to carry on

exit(0) #exiting the program at the break of the while loop