Python: for loop outside of while loop not working as expected

Question

I want to get how many attempts have been made before a random value between 0 and 10 is greater than 8. I have the following code which works correctly:

import numpy as np

x = np.random.uniform(low=0, high=10, size=1)
attempt = 1

while(x < 8):
    attempt = attempt + 1
    x = np.random.uniform(low=0, high=10, size=1)

However, now I want to get the number of attempts before x was greater than 8 for the fourth time. To do this, I placed the for loop just before the while loop which becomes like this:

for i in range(0,4):
    while(x < 8):
        attempt = attempt + 1
        x = np.random.uniform(low=0, high=10, size=1)

However, this is not working as I intended it to be. Can someone help me solve this problem?

this is not working as I intended it to be is hardly any useful information. What did you intend it to be? What did it actually do? — iBug
– iBug, Commented Feb 6, 2019 at 5:46
You never reset x so once x > 8 it stays that way for every interation of your for loop. Put x=0 between your for and your while. — Loocid
– Loocid, Commented Feb 6, 2019 at 5:47

taurus05 · Accepted Answer · 2019-02-06 05:56:02Z

2

You want to get the total number of attempts needed to obtain a random number 8 in 4 consecutive trails. Try this:

>>> import numpy as np
>>> def fun():
...     x = np.random.uniform(0,10,1)
...     attempt = 1
...     while x<8:
...             attempt += 1
...             x = np.random.uniform(0,10,1)
...     return attempt 
>>> for i in range(0,4):
...     print("Trial" , i , "took" , fun(), "Attempts")

Output:

Trial 0 took 1 Attempts
Trial 1 took 1 Attempts
Trial 2 took 8 Attempts
Trial 3 took 3 Attempts

answered Feb 6, 2019 at 5:56

taurus05

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2 Comments

thepoetdj Over a year ago

Can you also explain why @Beatrice's solution didn't work?

taurus05 Over a year ago

@DhruvJoshi, Beatrice's code works perfectly fine, but the only issue was that it wasn't generating the expected outcome.

hoodakaushal · Accepted Answer · 2019-02-06 05:49:10Z

0

The problem is that you're not resetting your x value. So once the variable is set to a value greater than 8, you code will not enter the while loop again. You need to set x = 0 before the while loop.

answered Feb 6, 2019 at 5:49

hoodakaushal

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Comments

brb · Accepted Answer · 2019-02-06 05:50:55Z

0

There are many ways of doing this. The below should work...

import numpy as np

successes = 0
rolls = 0
while (successes < 4):
    x = np.random.uniform(low=0, high=10, size=1)
    rolls += 1
    if x > 8:
        successes += 1

print(rolls)

answered Feb 6, 2019 at 5:50

brb

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Comments

Fatih1923 · Accepted Answer · 2019-02-06 06:37:56Z

0

This is not a for loop case. Try this:

while x < 8 and i <= 4:
    x = np.random.uniform(low=0, high=10, size=1)
    if x>8:
        i+=1
        x=np.random.uniform(low=0, high=10, size=1)
        attempt = 1
    print(attempt, x)
    attempt = attempt + 1

edited Feb 6, 2019 at 6:37

answered Feb 6, 2019 at 5:52

Fatih1923

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1 Comment

brb Over a year ago

This won't work. OP needs 4 rolls above 8 not 4 rolls in total.

paradocslover · Accepted Answer · 2020-05-17 08:31:04Z

0

You should modify your code to

for i in range(0,4):
    x = np.random.uniform(low=0, high=10, size=1)
    while(x < 8):
        attempt = attempt + 1
        x = np.random.uniform(low=0, high=10, size=1)

This would reset x before it enters into the while loop. Without this statement, your the control enters into the while loop only once.

edited May 17, 2020 at 8:31

answered Feb 6, 2019 at 5:50

paradocslover

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