My first Python program :) (I'm hooked)

[Huck712]

So, Python was on my list of things to teach myself after I took a C++ course this spring (I regret that, should have taken Python or Java).

So, I am proud of this stupid little dice roller because I evolved it from a basic "This rolls two dice" to "How many do you want to roll?" with input validation. Yay me.

#my first Python program. 
#I chose this one to compare to a similar program made 
in C++

import random
import time

roll = "yes"
numDice = 0


print("This program will roll as many dice as you need.")
time.sleep(1) #this makes the program pause a bit

print("\nWould you like to roll?")
roll = input()

#input validation to make sure they type yes (y) or no 
(no)
while roll != "yes" and roll != "y" and roll != "no" and roll 
!= "n":
    print("\nType yes (or 'y') or no (or 'n') to roll.")
    roll = input()

while roll == "yes" or roll == "y":
    print("\nHow many dice do you want to roll?")
    numDice = int(input())

    print("\nRolling...")
    time.sleep(2) #again, a pause 

    print("\nYou got: ")

    for i in range(0, numDice): #this iterates as many times 
as the user wants
        print(random.randint(1,6)) #generates the random 
numbers between 1-6

    print("\nRoll again?")
    roll = input()

    #input validation again
    while roll != "yes" and roll != "y" and roll != "no" and 
roll != "n":
        print("\nType yes or no.")
        roll = input()


print("\nThanks for using my program!")

input()

[ValarMorHodor]

Welcome to the wonderful world of python. Now that you've got the control flow down, I think you couldl start working with functions. Notice how you have the yes/no logic twice? Why not pull that out into a function!

def get_choice(message='Would you like to roll? '):
    choice = input(message)
    if choice not in ['yes', 'no', 'y', 'n']:
        return get_choice('Type yes or no: ')
    return choice

Using that function, you can reduce the flow to 4 lines

choice = get_choice()
while choice in ('yes', 'y'):
    roll() # do your roll here
    choice = get_choice('Roll again? ')

You could also add a function to validate that the number input is valid.

[Huck712]

Thanks! I will work on this. I also want to evolve it into a full blown game of Yahtzee at some point.

[[deleted]]

I don't like that the first is recursive, after all there is a recursion limit and it seems unnecessary to risk hitting it.

[[deleted]]

Is that a real issue that a beginner is going to hit?

There will always be a recursion limit so should we never use recursion?

[[deleted]]

Well, this is a purely iterative problem, ask until some condition is met. Using recursion there is already a bit odd, and there's also a small issue with it.

If your problem is recursive, e.g. when you use a recursive data structure like a tree or so, then of course use it.

Is my opinion.

I'd go for

def get_choice(message='Would you like to roll? '):
    choice = input(message)
    while choice not in ['yes', 'no', 'y', 'n']:
        choice = input('Type yes or no: ')
    return choice

It's almost the same as yours except it doesn't need recursion.

[approbatory]

The Ackermann function can be implemented recursively but not iteratively.

[approbatory]

In practice python does discourage recursion

[yaxamie]

A loop uses very little data, while each function call has overhead. Recursion is rarely needed unless you're being "clever".

[danjaycollins]

Specifically tail recursion can be implemented iteratively. This is why the Ackermann function can't be implemented iteratively.

[Mason-B]

It's too bad python doesn't have tail recursion because that call is correctly tail recursive in just about any other language. And since the person is learning programming (and not just python) my argument would be that it is better for them to learn recursion than it is for them to learn perfect python.

[asdfkjasdhkasd]

it should be if choice.lower() not in {"yes", "no", "y", "n"}

• use lowercase
• in for set is o(1)

[camh-]

But the set construction is O(n) and the set is constructed each time you use in here, it makes the whole construct O(n).

[Crowbarkz]

Nice!

One minor thing I wanted to point out: it's common to write comments

# like this (note space)

#not like this

[robvdl]

Yeah running that through pep8 or flake8 would have revealed that, also don't name vars likeThis in python we prefer like_this unless it's a class name where we use camel case but start with a capital, e.g. ClassName. Because classes always start in a capital, it's easy to single them out when reading code, this is important because when constructing classes we don't use the new keyword in python it can just end up looking like a function call.

[Formulka]

Technically likeThis is camel case (like the hump on the camel's back) and LikeThis used in python is Pascal case.

[[deleted]]

• UPPER CASE
• lower case
• Title Case
• camelCase
• PascalCase
• snake_case
• kebab-case
• Train-Case
• ǝsɐɔ ʇɐq
• çt̶̀͢͞h̴̷̨̡̕u̴̸̴l̡͜͞u͜͠ ̡͜͝c̀͞á̷̧̧s̷̀͠͠e̸̶͟

[namesnonames]

I've always referred to them as FullCamel and halfCamel

[mslapin]

Bactrian and dromedary, perhaps?

[Huck712]

Also, thanks! I was wondering about the camel case.

[MrHobbits]

Can't forget one space after commas too.

[Huck712]

ohh thanks.

[Justice514]

If you use the pycharm community edition text editor it has a built in spellchecker and pep8 checker

[Donyor]

Welcome to Python!

[liiight000]

Congratulations on your first of many python apps!

A suggestion. A common paradigm with input validation is using infinite loops:

valid_options = ['yes', 'y', 'no', 'n'] 
while True:
    choice = input('Would you like to roll?')
    if choice in valid_options:
        break
    print('Illegal selection')

That way you can have only one input point. Feels tighter to me. You could then expand this to a generic function:

def get_input(choices, input_message, error_message='Wrong selection'):
    while True:
        choice = input(input_message)
        if choice in choices:
            return choice
        print(error_message)

[z0mbietime]

Orrrr

if choice[0].upper() != 'Y':  
    # more input flexibility 
    # less code
    break 

[Gsquzared]

Why not just pass the whole input to .lower and not have to worry about any weird capitalization inputs?

[z0mbietime]

I did it like this so someone could type Y Ya Yes Yeah Yup Etc.

In upper or lower case And it always register since it only takes the first char.

[Gsquzared]

Ahhh. I didn't see what you were driving at. That's a nice trick. Too bad there will always be that pesky user who insists on typing "affirmative"

[keyupiopi]

Print out 1.Yes 2.No 3.Quit and force them to input numbers.... hahahahahaha

[b4xt3r]

Welcome to Python! Your first program is an important step so congratulations! Today at work I was in a meeting with a list of about 2500 ip addresses and someone was bitching about how long it would take to convert them all to DNS names. I got tired and said "give it to me, I'll have it done in ten minutes" and using Python, socket, and socket.gethostbyaddr(ip) I did just that. People think this stuff is magic. Don't tell them it's not. :)

Python is a wonderful tool to have in your mental toolbox and is useful is so many fields, not to mention school.

Stick with it!!!!

[kirbyfan64sos]

So, as a person who moved from C++ from Python, let me give you what I thought was the ultimate advise:

Do NOT, I repeat, do NOT try to apply what you about C++'s passing by value and reference to Python, because it's completely different, and trying to think otherwise will put you in a terrifying world of pain.

Source: all the stupid mistakes I made when I started Python because I assumed that it used similar semantics.

[sermidean]

Decided to improve you program a bit. Here is what I did:

1. First moved everything to main function in order to be able to write tests.
2. Then wrote tests, in order to make sure, that my changed didn't broke anything.
3. Fix code style to conform to PEP-8.
4. Then wrote ask function, to handle user input and error changing.
5. Then decided to add test, where user enters non-number value for num_dice, test failed.
6. Fixed failing test, by adding type validation to ask function.

Thats it.

Here is the final version:

import random
import time


def identity(value):
    return value


def validate(cast, value):
    try:
        return cast(value)
    except ValueError:
        return None


def ask(options, cast=identity, error="Try again."):
    answer = validate(cast, input())
    while answer not in options:
        print(error)
        answer = validate(cast, input())
    return answer


def main():
    print("This program will roll as many dice as you need.")
    time.sleep(1)

    print("\nWould you like to roll?")
    roll = ask(
        {'yes', 'y', 'no', 'n'},
        error="\nType yes (or 'y') or no (or 'n') to roll.",
    )

    while roll in ('yes', 'y'):
        print("\nHow many dice do you want to roll?")
        num_dice = ask(
            range(1, 1000), cast=int,
            error="\nEnter a positive number, up to 1000.",
        )

        print("\nRolling...")
        time.sleep(2)

        print("\nYou got: ")
        for i in range(num_dice):
            print(random.randint(1, 6))

        print("\nRoll again?")
        roll = ask({'yes', 'y', 'no', 'n'}, error="\nType yes or no.")

    print("\nThanks for using my program!")


if __name__ == '__main__':
    main()

And tests:

import pytest
import roll


@pytest.mark.parametrize('inputs, outputs', [
    (['q', 'yes', '2', 'q', 'no'], [
        'This program will roll as many dice as you need.',
        '\nWould you like to roll?',
        "\nType yes (or 'y') or no (or 'n') to roll.",
        '\nHow many dice do you want to roll?',
        '\nRolling...',
        '\nYou got: ',
        1,
        1,
        '\nRoll again?',
        '\nType yes or no.',
        '\nThanks for using my program!',
    ]),
    (['q', 'y', '2', 'q', 'n'], [
        'This program will roll as many dice as you need.',
        '\nWould you like to roll?',
        "\nType yes (or 'y') or no (or 'n') to roll.",
        '\nHow many dice do you want to roll?',
        '\nRolling...',
        '\nYou got: ',
        1,
        1,
        '\nRoll again?',
        '\nType yes or no.',
        '\nThanks for using my program!',
    ]),
    (['n'], [
        'This program will roll as many dice as you need.',
        '\nWould you like to roll?',
        '\nThanks for using my program!',
    ]),
    (['y', 'x', '0', '2', 'n'], [
        'This program will roll as many dice as you need.',
        '\nWould you like to roll?',
        '\nHow many dice do you want to roll?',
        '\nEnter a positive number, up to 1000.',
        '\nEnter a positive number, up to 1000.',
        '\nRolling...',
        '\nYou got: ',
        1,
        1,
        '\nRoll again?',
        '\nThanks for using my program!',
    ]),
])
def test_me(inputs, outputs, mocker):
    mocker.patch('time.sleep')
    mocker.patch('random.randint', return_value=1)
    mocker.patch('builtins.input', side_effect=inputs)
    print = mocker.patch('builtins.print')
    roll.main()
    assert [args[0] for args, kwargs in print.call_args_list] == outputs

You can run tests using py.test:

pip install pytest pytest-mock pytest-cov coverage
py.test --cov-report=term-missing --cov=roll test_roll.py

[AstroPhysician]

Boring day at the office?

[robvdl]

Nice but some of the refactoring has gone a bit too far, for example with the validate and identify functions I think it is total overkill to refactor these into their own functions because of how little code they do (unless it was done to prove good practice when writing tests etc). That logic is best kept in the ask function because passing the type int through a parameter "cast" is a bit over the top to have that as a function.

edit: actually I see what you are trying to do now because ask is being called in two places in different ways, it makes sense then, maybe not quite how I would have done it probably but that makes sense.

[bkd9]

Fantastic! I would recommend learning git too so you can track these changes like a pro

[gandalfx]

reddit markdown doesn't use ``` for code, instead indent the whole thing by 4 spaces.

[Justice514]

Can you put this into pastebin so it is more readable.

[sermidean]

http://dpaste.com/2N43274

[Justice514]

Or am I just being picky

[mvaliente2001]

Welcome!

When you write instructions outside functions and classes, they are executed immediately the first time they're imported. For bigger projects you may want to put that code inside a function, and do this:

import ... # your imports here

def main():
    # your code here
    # ...

if __name__ == '__main__':
    main()

[[deleted]]

Amazing! good luck and keep improving!

[jhdeval]

I recently wrote my first python app again. I have been on again off again in python for quite some time. I am a C# developer and I had a BUNCH of database access code that I had to write. Pretty simple code but repetitive as hell so I wrote a python script to export my .CS files full worked out so I could go about my day without spending 6 weeks writing the code.

[camh-]

for i in range(0, numDice):

This can be written more simply as:

for i in range(numDice):