Build a Probability Calculator Project - Build a Probability Calculator Project

Python
1

Tell us what’s happening:

I’m struggling with the 3rd test on this project. I’ve looked at other people’s code on the forum but I can’t see where I’m going wrong. I am also unable to find the test data that this test uses (I’ve tried using F12 but I can’t find the data). Any help would be appreciated!

Your code so far

import copy
import random

class Hat:
    def __init__(self,**kwargs):
        self.contents = []
        for kwarg in kwargs:
            for i in range(kwargs[kwarg]):
                self.contents.append(kwarg)

    def draw(self,no_draws):
        removals = []
        if no_draws > len(self.contents):
            return self.contents
        
        for i in range(no_draws):
            selection = random.choice(self.contents)
            self.contents.remove(selection)
            removals.append(selection)
        return removals
        
def experiment(hat, expected_balls, num_balls_drawn, num_experiments):
    success = 0
    
    for i in range(num_experiments):
        sacrificial = copy.deepcopy(hat)
        results = sacrificial.draw(num_balls_drawn)
    
        valid = True
        for colour in expected_balls:
            if results.count(colour) < expected_balls[colour]:
                valid = False
                break
        if valid:
            success += 1
        
    prob = success/num_experiments
    return prob

Your browser information:

User Agent is: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/128.0.0.0 Safari/537.36

Challenge Information:

Build a Probability Calculator Project - Build a Probability Calculator Project

2

For some reason my code passes if I deepcopy the self.contents into a new list and then clear self.contents and return the deepcopy. Can someone explain why this works and my original code didn’t?

3

Don’t know what your original code was but it is only deepcopy() that creates a new instance. The other copy methods only create a new reference to the same instance. If you update the new reference, you actually update the original instance. With deepcopy() you have a new instance so you update that instance while the original instance stays intact.

Hope this helps

4

Think of a physical hat. If you draw all of the balls out of the hat, how many balls remain in the contents of the hat?

5

Thanks! This way of thinking about it makes much more sense.

1 Like