Alternative to recursion?

Question

I'm starting to learn Python. Right now I'm creating a CLI that allows to create, view or delete contacts stored in a SQLite 3 DB. The problem is that everytime I finish a task I call the main function again so a user can do other things. The code looks like this:

def main(self):
    print("What operation would you like to perform: Display contacts (1), add a new one (2), or remove one  (3)?")
    option = int(input())
    try:
        if option == 1:
            self.display()
            self.main()
        elif option == 2:
            self.new()
            self.main()
        elif option == 3:
            self.delete()
            self.main()
    except TypeError:
        print("Please introduce a valid option")
        sys.exit()

I'm pretty sure that successive calls of a function decrease its performance and I think there is a limit of how many times you can call a recursive function, so how should I call the main method again?

Use a loop to repeat all the contents of main while option == 1 — pho
– pho, Commented Mar 31, 2021 at 18:28
Your except clause will never be hit. Did you intend for the option = int(input()) line to be inside the try? You know, you don't really need to incur the cost of exceptions there. You can say if option == '1': and skip the conversion to integer. — Tim Roberts
– Tim Roberts, Commented Mar 31, 2021 at 18:33

Vollfeiw · Accepted Answer · 2021-04-01 07:45:18Z

1

You're right about recursive calls. They can be good, but iteration is often better than recursion.

There's a lot that you can do to do infinite programm, but the easiest way, for cli, is to put all your function in a loop.

This is kinda ugly, but that should work without you having to call for main() everytime.

def main(self):
    again=True
    while again:
        print("What operation would you like to perform: Quit(0) Display contacts (1), add a new one (2), or remove one  (3)?")
        option = int(input())
        if option == 0:
            again=False
        if option == 1:
            self.display()
            self.main()
        elif option == 2:
            self.new()
            self.main()
        elif option == 3:
            self.delete()
            self.main()
        else:
            print("Please introduce a valid option")

With that said, you still have to call main()

edited Apr 1, 2021 at 7:45

answered Mar 31, 2021 at 18:49

Vollfeiw

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3 Comments

mkrieger1 Over a year ago

continue is a keyword and can't be used as variable name or expression.

juanpa.arrivillaga Over a year ago

continue=True is a syntax error, continue is a keyword

Xiddoc Over a year ago

You still have the continue keyword in your code, at continue=False

Giovane Boaviagem · Accepted Answer · 2021-03-31 19:32:26Z

-1

You can use argument libraries like getopt or argparse

The main goal here is manage the options inside a loop and call it all at once. Ex:

$ python3 ./script.py -123

answered Mar 31, 2021 at 19:32

Giovane Boaviagem

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Comments

r1v3n · Accepted Answer · 2021-03-31 18:50:34Z

-2

In python there is no such thing as "main function" or "main method". If you want, you can read about constructors, call operations and etc. So, if I understood correctly - you want to recursive call "main" method.

You can count occurrences in this method like this: def main(self, count= <your number>): And after this, if you want to call this recursive, create loop or just sum "count":

<some code here>
if count == <your number>:
    return
else:
    count += 5
self.main(count)

edited Mar 31, 2021 at 18:50

answered Mar 31, 2021 at 18:44

r1v3n

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1 Comment

juanpa.arrivillaga Over a year ago

I didn't downvote, but it sounds like the OP is asking exactly the opposite, i.e. how not to use recursion here

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