Probability Calc - experiment part

Python
1

I almost finished the task but in the experiment function i can’t put list with draw balls inside for loop to get everytime new result. (i got value error)

import copy
import random
# Consider using the modules imported above.

class Hat:
    
  def __init__(self, **args):
    self.contents = list()
    for v,k in args.items():#n-times add color ball
      self.contents += k*[v]
       
  
  def draw(self, num_balls):
    if(num_balls > len(self.contents)):
      return self.contents
    else:
      drawballs = list()
      for k in range(num_balls):
        
        drawballs.append(self.contents.pop(random.randint(0, len(self.contents)- 1 - k)))
      return drawballs


def experiment(hat, expected_balls, num_balls_drawn, num_experiments):
  expect = list()
  balls = copy.deepcopy(hat)
  allballs = balls.draw(num_balls_drawn)
  for v,k in expected_balls.items():
    expect += k * [v]

  m = 0
  for i in range(num_experiments):
    #allballs = balls.draw(num_balls_drawn)
    if(all(x in allballs for x in expect)):
      m += 1
  
  print(m)
  prob = m / num_experiments
  return prob
2

What exactly is the error? Could you copy the complete traceback?

3 
Traceback (most recent call last):
  File "main.py", line 6, in <module>
    probability = prob_calculator.experiment(
  File "/home/runner/boilerplate-probability-calculator/prob_calculator.py", line 33, in experiment
    allballs = balls.draw(num_balls_drawn)
  File "/home/runner/boilerplate-probability-calculator/prob_calculator.py", line 20, in draw
    drawballs.append(self.contents.pop(random.randint(0, len(self.contents)- 1 - k)))
  File "/usr/lib/python3.8/random.py", line 248, in randint
    return self.randrange(a, b+1)
  File "/usr/lib/python3.8/random.py", line 226, in randrange
    raise ValueError("empty range for randrange() (%d, %d, %d)" % (istart, istop, width))
ValueError: empty range for randrange() (0, 0, 0)
exit status 1

4

I’m assuming the error occurs when that line isn’t commented out. Notice that function uses the same, one hat for all experiments.

1 Like
5

Error occurs when variable allballs with ball drawed from the one and only hat object is inside for loop and only when it is there i got every time different set of balls which is right but in
if(all(x in allballs for x in expect)):

i got error which lead to random.py code error line

raise ValueError("empty range for randrange() (%d, %d, %d)" % (istart, istop, width))```.
And when var out of for loop the is the same so test fails.
6

Take a closer look at the experiment description in README.md file, each test should start with hat being filled with the same balls.

1 Like
7

The hat is the same (the first argument) but every time you draw balls from it you need to get different results this is why i’m trying to put var allballs inside for loop but error appears

8

Let me write it differently - error is because after few experiments no ball is left in the hat.

Different result of the draw comes from fact of using random module for drawing balls, not because after each experiment different number of balls is left in hat for next experiment.

1 Like
9

Oh, i got you. Now after moving hat copy inside for loop i got not 100% probability though still too high (0.843).

Thanks a lot. I’ll try to finish it tomorrow

11

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