[FIXED] Inputting a number and outputting a name?

Issue

OK so I have this task at school, I'm a complete beginner but I have most of it down, I need to ask for the number and have it output the corresponding name (it's part "d") I managed to get part C to work but when I try to do the same thing to D it refuses to work. I know I'm probably doing something wrong but as I said I'm a complete beginner.

Also, can I tried changing my c+d to "if" so that I could add another "else" so that if the name/number that was input wasn't in any of the lists that it would return saying "invalid" but I cant seem to be able to change them to if statements.

Anyway here's the code I'm trying to make work, like I said, C works but D refuses to:

flag="F"
choice=""

#Looping-----------------------------------------------------------------------

while choice != "F" and choice !="f":
    print( " A. Setup Name, Number and CallsPerDay \n"
           " B. Display all names and numbers \n"
           " C. Insert name to find out number \n"
           " D. Insert number and find out name \n"
           " E. Display Min, Max and Average CallsPerDay \n"
           " F. Finish the Program")

    choice=input("Select an option: \n\n")

#Selection---------------------------------------------------------------------

    if choice=="A" or choice =="a":
        if flag=="F":
            names=["gordon", "david", "graeme", "joyce", "douglas", "brian", "suzanne", "karen"]
            numb=[273429, 273666, 273512, 273999, 273123, 273224, 273324, 273424]
            CPD=[30, 10, 15, 2, 5, 1, 3, 6]
            length=len(numb)
            print("Names, Numbers and CallsPerDay have now been set up \n")
            flag="T"
        elif flag=="T":
            print("Lists already set up \n")

#---------------------------------------------------------------------------------

    elif choice=="B" or choice=="b":
        if flag=="F":
            print('Run option A first!')
        else:        
            for i in range(0,length,1):
                print(names[i],numb[i], CPD[i], "\n")

#-------------------------------------------------------------------------------

    elif choice=="C" or choice=="c":
        if flag=="F":
            print('Run option A first!')
        else:
            wanted=input('Name please ').lower()
            i=0
            while names[i] != wanted:
                i=i+1
            print('Number',numb[i])



#----------Part that refuses to work------------------------

    elif choice=="D" or choice=="d":
        if flag=="F":
            print('Run option A first!')
        else:
            wanted=input('Number Please: ')
            i=0
            while numb[i] != wanted:
                i=i+1
            print('Number',names[i])

Here is the error I get in the shell when trying to do this:

 A. Setup Name, Number and CallsPerDay 
 B. Display all names and numbers 
 C. Insert name to find out number 
 D. Insert number and find out name 
 E. Display Min, Max and Average CallsPerDay 
 F. Finish the Program
Select an option: 

a
Names, Numbers and CallsPerDay have now been set up 

 A. Setup Name, Number and CallsPerDay 
 B. Display all names and numbers 
 C. Insert name to find out number 
 D. Insert number and find out name 
 E. Display Min, Max and Average CallsPerDay 
 F. Finish the Program
Select an option: 

d
Number Please: 223666
Traceback (most recent call last):
  File "G:\Lvl 5\sofware\menuNEWex - Copy.py", line 62, in <module>
    while numb[i] != wanted:
IndexError: list index out of range
>>> 

It should be outputting David, because they are both #2 on their lists

Solution

There's a few problems here. First, you need to convert wanted from a string to an integer so your comparison will work:

# Not this, because the return of input is a string
wanted=input('Number Please: ')

# But this. Note this will throw a ValueError if converting to an int fails!
wanted = int(input('Number please: '))

# This one has error handling!
try:
    wanted = int(input('Number please: '))
except ValueError:
    print("That's not a number")

Also, if your entered number is not in your list numb, your loop will still break when i becomes larger than the last index. Try using the index method instead, as it will either return the index of the number or throw a ValueError. Be careful though - that index is the first index of the element in the list. If the same number is repeated, you'll need another approach that handles conflicts:

try:
    i = numb.index(wanted)
    print('Number', names[i])
except ValueError:
    print("No such number")

You should also consider wrapping your input requests in while loops that look for valid values. For example, you need a number for the above section:

i = None
while i is not None:
    try:
        i = int(input("Number: "))
    except ValueError:
        # i is still None
        print("Must enter a number!")

An example running would give you this:

Number: a
Must enter a number!
Number: b
Must enter a number!
Number: 33

If you put checking your index in that loop, you get checking for integers and valid values at the same time.

Answered By - thegrinner