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Multiple list edit and output

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Yoink
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26 posts since Feb 2012
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I'm a beginner with python and I'm trying to write a program that asks the user for how many classes they have taken, then asks them for the class codes and prints the classes they have left to take.

I can get the program to run perfectly for one list but the trick is there are 3 lists. I made listA the computer science courses which has to print with a header of "part A requirements" and then print each item in the list on a separate line.

The part I am stumped on is removing items from the other separate lists all from one user input, and then printing each list showing what requirements are left for each.

def main(): 
    print "This program returns a list of classes you still have to take: "
    classlistA = ["CMSC 201", "CMSC 202", "CMSC 203", "CMSC 304", "CMSC 313",
                 "CMSC 331", "CMSC 341", "CMSC 345", "CMSC 411", "CMSC 421",
                 "CMSC 441"]
    classlistB = ["MATH 151", "MATH 152", "MATH 221"]
    classlistC = ["STAT 334" ,"STAT 451"]
    classname = input ("How many classes have you taken so far?: ")
    
    for i in range(classname):
        classname = raw_input("Please type the classes you have taken <CODE><COURSE-NUMBER>: ")
    classlistA.remove(classname)

    
    
    print "part A requirements"
    for x in classlistA:
        print "You still have to take", x


main()
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hughesadam_87
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274 posts since May 2009
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There are numerous solutions to this problem, but perhaps one that is most straightforward is to just put all your items in a list of lists. Or a tuple of lists, or a dictionary of lists...etc there's many advanced storage options in python.

Here's a list of lists:

def main(): 
    print "This program returns a list of classes you still have to take: "
    classlistA = ["CMSC 201", "CMSC 202", "CMSC 203", "CMSC 304", "CMSC 313",
                 "CMSC 331", "CMSC 341", "CMSC 345", "CMSC 411", "CMSC 421",
                 "CMSC 441"]
    classlistB = ["MATH 151", "MATH 152", "MATH 221"]
    classlistC = ["STAT 334" ,"STAT 451"]

    all_lists=[ classlistA, classlistB, classlistC]

    classname = input ("How many classes have you taken so far?: ")
    
    for i in range(classname):
        classname = raw_input("Please type the classes you have taken <CODE><COURSE-NUMBER>: ")
    for classlists in all_lists:
        try classlists.remove(classname)
    except Exception:
        print 'cannot remove that, not found'
        pass
    
    
    print "part A requirements"
    for x in classlistA:
        print "You still have to take", x


main()

What I did was I just put your 3 classlists in a new list called all_lists. Then I also put in an error exception that will handle the situation when you try to remove an element that is not there.

Again, there are many more elegant solutions.

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Yoink
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Ill mess around with that idea and see what I can do. Thanks!

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I tried out a multiple ways of doing lists of lists and the one problem I'm running into now is when I go to print out the remaining items in each list. I have to print them in the format of

"part A requirements"
CMSC<number>...

"Part B requirements"
MATH<number>...

etc.

Because I am making a list of lists, I am only editing the big list, not the individual ones, so when I go to print out only the specific items for each part such as partA, partB, and partC, I still print out every item.

Is there a way to separate out each newly edited list from the bigger allLists so that I can print each part separately? Here is my new code so far

print "This program returns a list of classes you still have to take: "
    classlistA = ["CMSC 201", "CMSC 202", "CMSC 203", "CMSC 304", "CMSC 313",
                  "CMSC 331", "CMSC 341", "CMSC 345", "CMSC 411", "CMSC 421",
                  "CMSC 441"]
    classlistB = ["MATH 151", "MATH 152", "MATH 221"]
    classlistC = ["STAT 334" ,"STAT 451"]
     
    allLists = (classlistA + classlistB + classlistC)
 
     
    classnumber = input ("How many classes have you taken so far?: ")
     
    for i in range(classnumber):
        classname = raw_input("Please type the classes you have taken <CODE> <COURSE-NUMBER>: ")
        allLists.remove(classname)
    
    
    print "part A requirements"
    for x in classlistA: ## will print out everything in classlistA without removing classes
        print "You still have to take", x

         
    print "part B requirements"
    for classlistB in allLists:## will print out everything allLists with classes removed
        print "You still have to take", classlistB
         
  ##  print "part C requirements"
  ##  for x in classListsC:
   ##     print "You still have to take", x
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hughesadam_87
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274 posts since May 2009
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Hmm, so the way you defined alllists, you did not make a list of lists; rather, you simply made a single list by adding all the items from your smaller lists together. To make a list of lists, you'd use this syntax:

alllists=[classlistA, classlistB, classlistC ]

Then I'd change the following line:

for i in range(classnumber):
       classname = raw_input("Please type the classes you have taken <CODE> <COURSE-NUMBER>: ")
       allLists.remove(classname)

To

for i in range(classnumber):
       classname = raw_input("Please type the classes you have taken <CODE> <COURSE-NUMBER>: ")
       for classlist in alllists:
           if classname in classlist:
               classlist.remove(classname)
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woooee
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2,792 posts since Dec 2006
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The simplest is to use a dictionary

classes_taken={classlistA:["CMSC 201", "CMSC 202", "CMSC 203"],
               classlistB:["MATH 151", "MATH 152"]}
etc.

If you want to use lists then you can just transfer the classes taken to the list, so you would have 3 classes_taken lists or one list with 3 sublists. You can also use one list in this way

print "This program returns a list of classes you still have to take: "
classlistA = ["CMSC 201", "CMSC 202", "CMSC 203", "CMSC 304", "CMSC 313",
              "CMSC 331", "CMSC 341", "CMSC 345", "CMSC 411", "CMSC 421",
              "CMSC 441"]
classlistB = ["MATH 151", "MATH 152", "MATH 221"]
classlistC = ["STAT 334" ,"STAT 451"]

# simulate this data was entered
test_data = ["CMSC 201", "CMSC 202", "STAT 334", "MATH 151", "MATH 152"]
set_test_data=set(test_data)

## print classes to be taken
letters = ["A", "B", "C"]
for ctr, classlist in enumerate([classlistA, classlistB, classlistC]):
    print "You have not taken the following classes in %s" % (letters[ctr])
    for this_class in classlist:
        if this_class not in test_data:
            print "     ", this_class

    print "\nEven easier with sets"
    print set(classlist).difference(set_test_data), "\n"
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Yoink
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Thanks, I used your suggestions and got it working correctly.

Question Answered as of 2 Years Ago by hughesadam_87 and woooee
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