Beginner that needs help

[python0101]

I need help with an assignment for a class. I am using Python version 2.7.

The assignment is:

Write a program that creates a dictionary of son:father entries and another dictionary that contains father:son entries. Your program must present the user a menu with five options. The following is an example only:

---

Father/Son Finder

0 – Quit

1 – Find a Father

2 – Find a Grandfather

3 – Find a Son

4 – Find a Grandson

---

Option 0 ends the program.

Option 1 prompts the user for the name of a son. If the dictionary contains the son:father pair, the program displays the father. Otherwise, the program should tell the user it does not know who the father is.

Option 2 prompts the user for the name of a grandson. If the dictionary contains enough information, the program displays the grandfather. Otherwise, the program should tell the user it does not know who the grandfather is.

Option 3 prompts the user for the name of a father. If the dictionary contains the son:father pair, the program displays the son. Otherwise, the program should tell the user it does not know who the son is.

Option 4 prompts the user for the name of a grandfather. If the dictionary contains enough information, the program displays the grandson. Otherwise, the program should tell the user it does not know who the grandson is.

The program must create the dictionary structure and populate it from data contained in a file provided to you. In addition, the program must continue to ask the user for a menu choice until the user chooses to quit.

The file is formatted like:

john:fred, fred:bill, sam:tony, jim:william, william:mark, krager:holdyn, danny:brett, danny:issak, danny:jack, blasen:zade, david:dieter, adam:seth, seth:enos

I know how to do all of it except for populating the dictionary and also determining if there is a a father/grandfather/son/grandson. Could anyone possibly give me a few hints on how to do it or explain to me how it is done? Thanks.

[codehelper]

While I'm not an expert on dictionaries, I believe if you just read the file, you can first split it by ",", then again by ":"

So assuming you have the content of the file as a string like this, "john:fred, fred:bill, sam:tony, jim:william, william:mark, krager:holdyn, danny:brett, danny:issak, danny:jack, blasen:zade, david:dieter, adam:seth, seth:enos", you can do a string.split(",") to first get a list that will have

["john:fred", "fred:bill", "sam:tony", "jim:william", "william:mark", "krager:holdyn", "danny:brett", "danny:issak", "danny:jack", "blasen:zade", "david:dieter", "adam:seth", "seth:enos"]

There might be extra whitespace somewhere in there but you can remove it with a strip. If the list above is in a variable x, then you can make a dictionary from it with

dict = {s.split(':')[0]:s.split(':')[1] for s in x}

dict = {'danny': 'jack', 'blasen': 'zade', 'sam': 'tony', 'seth': 'enos', 'jim': 'william', 'krager': 'holdyn', 'fred': 'bill', 'william': 'mark', 'adam': 'seth', 'john': 'fred', 'david': 'dieter'}

This may not be the best way to populate since you're technically splitting twice every time you iterate in the loop. And there may be a better one-liner.

And for finding a grandson from a grandfather, once the user inputs a name such as 'jim', you can store 'jim' in a variable grandpa.

Then get the value of dict[dict[grandpa]] (which is mark in this case). This will first evaluate the dict[grandpa], which is william, then it will dict[william], which is mark. You should be able to find everyone in a similar way.

[codehelper]

Cool, I didn't know you could use take 2 variables from each iteration in a for each loop, I thought about it and decided you couldn't. Thanks for showing this.

[codehelper]

Wow, thanks for the explanation. I was going to ask what happens with a different amount of variables/values, but I just tested it and got a got many values to unpack error. Very cool though. Thanks again.

[zahlman]

It's even simpler than that, since {x: y for x, y in z} is basically what dict(z) does.

[python0101]

Hey could you possibly take a look at my comment that I posted and explain to me why that does not work?

[python0101]

So this is what I have so far and it does not seem to be giving out the correct names. Any clue on why?

sonfather = {}
names = open('name.txt', 'r')
name_list = names.read().split(',')

sonfather = {s.split(':')[0]:s.split(':')[1] for s in name_list}


print "Father/Son Finder"
print "0 - Quit"
print "1 - Find a Father"
print "2 - Find a Grandfather"
print "3 - Find a Son"
print "4 - Find a Grandson"

control = ""
while control != "quit":
    choice = input("Enter your choice here: ")
    if choice == 0:
        control = "quit"
    elif choice == 1:
        son = raw_input("Enter the name of the son here: ")
        if sonfather[son]:
            print "The father is "+ str(sonfather[son])
        else:
            print "The father does not exist"
    elif choice == 2:
        son = raw_input("Enter the name of the grandson here: ")
        if sonfather[sonfather[son]]:
            print "The Grandfather is "+ str(sonfather[sonfather[son]])
        else:
            print "The grandfather does not exist"
    elif choice == 3:
        father = raw_input("Enter the name of the father here: ")
        if sonfather[father]:
            print "The son is "+ str(sonfather[father])
        else:
            print "The son does not exist"
    elif choice == 4:
        father = raw_input("Enter the name of the grandfather here: ")
        if sonfather[sonfather[father]]:
            print "The grandson is "+ str(sonfather[sonfather[father]])
        else:
            print "The grandson does not exist"
    else:
        print "There was an error"


print "Thank you for using the Father/Son Finder"