Question

I am new to python (and programming in general) and am making a database/register for a typical class. I wanted the user to be able to add and remove pupils from the database, I used lists primarily for this but have hit a stump.

Whenever I restart the program the list the user has modified returns back to the defualt list I specified in the code. I looked around the internet and tried to save the list onto a seperate txt file. However the txt file also goes back to the defualt every time I restart the program. I would like you to please give me a way to save the changes made to the list and keep them that way. Here is the code (it’s not very good):

def menu():
    print "*****************CLASS REGISTER*****************"
    print "Press 1 See The List Of Pupils"
    print "Press 2 To Add New Pupils"
    print "Press 3 To Remove Pupils"
    print "Press 0 To Quit \n"

filename = open('pupil.txt','r')

pupil = ["James Steele", "Blain Krontick", "Leeroy Jenkins", "Tanvir Choudrey"]

def see_list(x):
    print x

def add_pupil(x):
    print "You have chosen to add a new pupil.\n"
    option = raw_input("Please type the childs name.")
    x.append(option)
    filename = open('pupil.txt','w') 
    filename.write('\n'.join(pupil)) 
    filename.close() 
    print option, "has been added to the system."
    return x

def delete_pupil(x):
    print "You have chosen to remove a pupil.\n"
    option = raw_input("Please type the childs name.")
    if option in x:
        x.remove(option)
        filename = open('pupil.txt','w') 
        filename.write('\n'.join(pupil)) 
        filename.close() 
        print option, "has been removed from the system."
    else:
        print "That person is not in the system."
    return x


one = 1
while one != 0:
    menu()
    option = input() 
    if option == 1:
        see_list(pupil)
    elif option == 2:
        add_pupil(pupil)
    elif option == 3:
        delete_pupil(pupil)
    elif option == 0:
        break
    else:
        print "That is not a valible choice."

filename = open('pupil.txt','w') 
filename.write('\n'.join(pupil)) 
filename.close() 


if option == 0:
    quit

Answer 1

Well, you just open the pupil.txt file but never read back its contents. You need something like this:

filename = open('pupil.txt', 'r')
contents = filename.read()
filename.close()

pupil = [name for name in contents.split('\n') if name]

Also, you will need to handle the case when the pupil.txt file does not exist; this can be done with a try..except block around the IO calls.

Finally, as one of the comments has mentioned above, have a look at the pickle module, which lets you store a Python object in a file in Python’s internal format (which is not really readable, but saves you a lot of hassle).