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Python SQLAlchemy Basics Working with SQLAlchemy Setting Up Our App

Posted by amandae
amandae
15,727 Points

While True clause causes an infinite loop.

Hi. In the video, Megan makes this loop. I've checked it several times to make sure it isn't a typo on my part. When she runs this loop, it shows the menu and question once and waits for input. When I run this code, the 1-5 menu options run infinitely until it throws and error, and never reaches the "choice" variable.

It actually makes more sense to me that an infinite loops would break this, and I can think of fixes, but I'm wondering why this runs the way she wants it to, but mine breaks. She starts this around 36 secs into the video, and runs the program at 1:50.

def menu():
    while True:
        print('''
        \nPROGRAMMING BOOKS
        \r1) Add a Book
        \r2) View All Books
        \r3) Search for a Book
        \r4) Book Analysis
        \r5) Exit
        ''')
    choice = input('What would you like to do?  ')
    if choice in [1, 2, 3, 4, 5]:
        return choice
    else:
        input('Please choose an option by its number (1-5), listed above.')

3 Answers

Mel Rumsey
.a{fill-rule:evenodd;}techdegree seal-36
Mel Rumsey
Treehouse Moderator

Hey amandae You are close! Currently your 

    choice = input('What would you like to do?  ')
    if choice in [1, 2, 3, 4, 5]:
        return choice
    else:
        input('Please choose an option by its number (1-5), listed above.')

is outside of your while loop. You'll need to make sure this code is inside of the loop! Otherwise, your code looks good! :)

amandae
amandae
15,727 Points
amandae
amandae
15,727 Points

<facepalm>
Thank you. It seems so easy once you say it!

For anyone else who can't see it...

When Megan writes her code, the choice = input... is a tab closer to the edge than the string above it. In my code, the two will be vertically aligned. This is simply a style difference between VSCode and PyCharm. Both are fine for the string, but it means PyCharm code will line up differently. I was moving this line of code back a tab, to match hers, while not noticing I was a tab back already.

Christopher Rodriguez
seal-mask
.a{fill-rule:evenodd;}techdegree seal-36
Christopher Rodriguez
Python Development Techdegree Graduate 11,265 Points
Christopher Rodriguez
.a{fill-rule:evenodd;}techdegree seal-36
Christopher Rodriguez
Python Development Techdegree Graduate 11,265 Points

I have a similar infinite loop (using pycharm). The way i solved this was to use break(at least for now). Not sure why this is hapennin as my indentation appear correct? please tell me if I'm wrong!

from models import (Base, session, Book, engine)

def menu():
    while True:
        print(''' 
            \nProgramming books
            \r1) Add book
            \r2) View all books
            \r3) Search for books
            \r4) Book analysis
            \r5) Exit''')
        choice = input('what would you like to do?')
        if choice in ['1', '2', '3', '4', '5']:
            return choice
            break
        else:
            print('\nChoose an option above! \nAnd press ENTER')

if __name__ == '__main__':
    Base.metadata.create_all(engine)
    menu()