Make a backwards phonebook from a regular phonebook

your function should take 2 parameters: infile and outfile

infile should be a phonebook in the same format as question 2 (version 2).

outfile should be a list of phone number people pairs, sorted by phone number

as with question 2, you should account for the possibility that 2 people may share a single phone number (e. g., a land line if they live in the same home)

first read in all phone numbers into a dictionary, the same as you had done for question 2. you can call functions defined in question 2 and use global variables from question 2 as well if it makes sense to do so.

read through that dictionary and create a backwards version.

in the new dictionary the keys are phone numbers and the values are lists of people

use a similar strategy as with version 2 of question 2:

if a number is not in the dictionary, you create a new entry which is a list of a single person

otherwise, you check the list associated with that number and you add a person's name if they are not already listed in the (backwards) phonebook

create a list of keys from the dictionary and sort it.

for each key in the list, look up the corresponding entry/

for each name in the entry (also a list), write a line in the output firle consisting of a telephone number + a tab + a name

for example, given the sample file

name phone number
bob 212-888-
bugs 917-433-
daffy 914-400-4141
daffy 800-999-
daisy 914-400-4141
daisy 123-456-7890
pippi 301-999-9990
pippi 800-333-4400
yosemite 212-333-
as input, the program would produce

telephone number name
123-456-7890 daisy
212-333- yosemite
212-888- bob
301-999-9990 pippi
800-333-4400 pippi
800-999- daffy
914-400-4141 daisy
914-400-4141 daffy
917-433- bugs
as output (notice that daffy and daisy share a phone number).