CODEWITHSUNDEEP
python
John
John

Reputation: 75

Counting random numbers

Suppose I repeatedly generate random integers from 0-9 until a given number comes out. What I need is a function that counts how many integers are generated until this happens. Please help me with this.

This is what I have tried, I put 1000 becasue it is big enough but I don't think it is correct because my number can come after 1000 iterations.

for i in range(1000):
  d = randint()
  if d <> 5:
     cnt = cnt + 1
  if d == 5:
     break

Upvotes: 4

Views: 6688

Answers (5)

elyase
elyase

Reputation: 40973

Suppose 5 is the number you are expecting:

sum(1 for _ in iter(lambda: randint(0, 9), 5))

You can add 1 if you want to include the last number.

Explanation:

  • iter(function, val) returns an iterator that calls function until val is returned.
  • lambda: randint(0, 9) is function (can be called) that returns randint(0, 9).
  • sum(1 for _ in iterator) calculates the length of an iterator.

Upvotes: 10

John La Rooy
John La Rooy

Reputation: 304235

itertools.count is often neater than using a while loop with an explicit counter

import random, itertools

for count in itertools.count():
    if random.randint(0, 9) == 5:
        break

If you want the count to include the iteration that generates 5, just start the count at 1 using itertools.count(1)

Upvotes: 2

dansalmo
dansalmo

Reputation: 11686

from random import randint
count = 0
while randint(0, 9) != 5:
   count += 1

Upvotes: 1

Blender
Blender

Reputation: 298246

A few things:

  • If you want your loop to continue until you stop it, use a while loop instead of a for loop.
  • You should use != as the inequality operator instead of <>.

Here's something to get you started:

import random

count = 0

while True:
    n = random.randint(0, 9)
    count += 1

    if n == 5:
        break

You could also write:

import random

count = 1
n = random.randint(0, 9)

while n != 5:
    count += 1
    n = random.randint(0, 9)

Converting it into a function is left as an exercise for the reader.

Upvotes: 9

user2555451
user2555451

Reputation:

This should work:

from random import randint
# Make sure 'cnt' is outside the loop (otherwise it will be overwritten each iteration)
cnt = 0
# Use a while loop for continuous iteration
while True:
    # Python uses '!=' for "not equal", not '<>'
    if randint(0, 9) != 5:
        # You can use '+=' to increment a variable by an amount
        # It's a lot cleaner than 'cnt = cnt + 1'
        cnt += 1 
    else: 
        break
print cnt

or, in function form:

from random import randint
def func():
    cnt = 0
    while True: 
        if randint(0, 9) != 5:
            cnt += 1 
        else: 
            break
    return cnt

Upvotes: 0

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