python change source code while running

Question

Simple questions for those who know, pretty hard for me, as I think that it is not pratically possible.

After making a simple python program, it is possible to run it on the computer's command prompt.

I was wondering or it is possible to allow someone who runs it that way, to add an element to a list (list.insert) and have it still there the next time the program is run?(thus editting the predefined list to a new list and saving it that way)

EDIT: just giving a bit more information:

All the program has to do is allow you to choose a list. From this list it returns a random item. I was just hoping to allow to add items to this list while running the program, keeping the list updated afterwards.

Answer 1

The most basic way is to use the Pickle module to save and load your data to disk:

http://docs.python.org/2/library/pickle.html

http://docs.python.org/2/library/pickle.html#example

Here's how I would use it in a simple program

try:
    import cPickle as pickle
except ImportError:
    import pickle

class MyClass(object):

    def __init__(self, file_name):
        self.array = []
        self.file_name = file_name
        self.load_data()

    def add_element(self, element):
        self.array.append(element)
        self.save_data()

    def load_data(self):
        try:
            with open(self.file_name, "r") as f:
                self.array = pickle.load(f)
        except IOError:
            pass

    def save_data(self):
        with open(self.file_name, "w") as f:
            pickle.dump(self.array, f)

def main():
    FILE_NAME = "test.pkl"
    a = MyClass(FILE_NAME)
    print "elements in array are", a.array
    for i in range(5):
        a.add_element(i)

if __name__ == "__main__":
    main()