any() in python coding issue

Question

I am trying to make a function that tells you if a number is prime or not using the any() method. This is what I have:

def prime(n):
    if any(n % i == 0 for i in range(1, n + 1)) != True:
        print("Prime")
    else:
        print("Not Prime")

prime(5)

However it is giving me:

Not Prime

every single time, even when I give a prime number.

Can someone please help me out?

As an aside from the answer already given, note that for any boolean b, if b != True would be written more idiomatically as if not b. — fuglede
– fuglede, Commented Jun 5, 2018 at 11:43

Carcigenicate · Accepted Answer · 2018-06-05 11:42:41Z

1

Everything is divisible by 1, so that check will consider everything as non-prime. You need to set the lower bound to check to 2 instead.

As pointed out in the comments by @ForceBru, the upper bound is incorrect as well. You don't want to check if n is divisible by itself, since it always will be.

Change your range in the comprehension to just:

range(2, n))

edited Jun 5, 2018 at 11:42

answered Jun 5, 2018 at 11:40

Carcigenicate

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4 Comments

ForceBru Over a year ago

Also, n % n == 0 as well.

domochevski Over a year ago

Then again why not put a not in front of the any and remove the != True. It would make things clearer.

Klaus D. Over a year ago

To significantly speed up the test for larger numbers you should stop checking above the square root of n.

Carcigenicate Over a year ago

All good points, but they kind of detract from the main problem.

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