On Sun, May 6, 2018 at 5:05 PM, Alan Gauld <alan.ga...@yahoo.co.uk> wrote: > On 6 May 2018, at 23:00, boB Stepp <robertvst...@gmail.com> wrote:
>>My understanding of best practice here is that I should not have any >>print() calls inside my generate_collatz_sequence() function. I >>_could_ store the generated sequence in a list and return it, but that >>does not seem like good use of RAM if some user-supplied seed value >>led to kazillions of Collatz sequence numbers being generated. > > The clue is in that last word. > Write a generator function that yields the intermediate results. Ok. I've been reading up on generators and playing around with them today. And then, per Alan's hint, tried to separate all display code from my program logic code. What was originally meant to be a throw-away effort, has somehow mushroomed into something I hope resembles a finished product. The results I came up with are as follows: #-------------------------------------------------------------------------------- #!/usr/bin/env python3 """This program will generate a Collatz sequence from a user-supplied positive integer. According to Wikipedia (https://en.wikipedia.org/wiki/Collatz_conjecture): "The Collatz conjecture is a conjecture in mathematics that concerns a sequence defined as follows: start with any positive integer n. Then each term is obtained from the previous term as follows: if the previous term is even, the next term is one half the previous term. Otherwise, the next term is 3 times the previous term plus 1. The conjecture is that no matter what value of n, the sequence will always reach 1." """ def get_positive_integer(): """Get a positive integer from the user.""" while True: try: integer = int(input("Please enter a positive integer: ")) if integer > 0: return integer else: print("That was not a positive integer!") continue except ValueError: print("That was not an integer!") continue def display_collatz_numbers(seed, collatz_generator): """Display a Collatz sequence, one value per line, given the seed (Which will be the first number in the sequence.) and a generator which will yield the Collatz sequence.""" print("\nThe seed number: ", seed) for sequence_index, number in enumerate(collatz_generator): print("Sequence number", sequence_index + 1, ": ", number) def ask_to_continue(): choice = input("Do you wish to generate another Collatz sequence?").lower() return choice.startswith('y') def get_collatz_number(integer): """Returns the Collatz sequence number corresponding to integer. integer must be > 0, or the sequence will not converge to 1.""" if integer % 2 == 0: return integer // 2 else: return 3 * integer + 1 def generate_collatz_sequence(seed): """Creates a generator, which will yield a Collatz sequence starting from seed. seed must be a positive integer, or the sequence will not converge to 1.""" collatz_number = seed while True: collatz_number = get_collatz_number(collatz_number) yield collatz_number if collatz_number == 1: return def main(): """Run program.""" while True: seed = get_positive_integer() display_collatz_numbers(seed, generate_collatz_sequence(seed)) if ask_to_continue(): continue else: break if __name__ == '__main__': main() #-------------------------------------------------------------------------------- Questions and comments: 1) I am open to a general critique on making this code better. 2) I spent a lot of effort trying to come up with a way to combine the two functions, get_collatz_number() and generate_collatz_sequence(), into something both more compact and more readable, but I was unsuccessful. I suspect there is a better way. Is there? And how would I do it? 3) Is this the correct way to separate display code from program logic code? Is there a better way to do this? 4) I think this is the first time I've actually tried to implement a generator function. Did I do a good Pythonic implementation of this? As always, thanks! -- boB _______________________________________________ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
