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+---- Thread: isprime function (/showthread.php?tid=4969)
isprime function - nevets04 - 02-23-2010
I made this function to check whether a number was prime or not.
This was developed using codepad.org to test it during my 15 minute study hall. So it's simple, but it does work as far as I can see.
Code:
#!/usr/bin/env python
def isprime(n):
if n > 10:
if n%2 == 0 or n%3 == 0 or n%4 == 0 or n%5 == 0 or n%6 == 0 or n%7 == 0 or n%8 == 0 or n%9 == 0 or n%10 == 0:
return False
else:
return True
if n <= 10:
if n == 2 or n == 3 or n == 5 or n == 7:
return True
if n == 1 or n == 4 or n == 6 or n ==8 or n == 9 or n == 10:
return FalseRE: isprime function - uber1337 - 02-23-2010
Seems to be effective, you could have shortened it a bit though
Code:
#!/usr/bin/env python
def isprime(n):
if n > 10:
for x in range(2, 11):
if n%x == 0: return False
else:
return True
if n <= 10:
if n in (2, 3, 5, 7): return True
if n in (1, 4, 6, 8, 9, 10): return False
RE: isprime function - Fallen - 04-05-2010
(02-23-2010, 06:46 PM)uber1337 Wrote:I can see your a little rustyCode:if n in (2, 3, 5, 7): return True
if n in (1, 4, 6, 8, 9, 10): return False
Code:
return False if n in [1, 4, 6, 8, 9, 10] else TrueYou are aswell
RE: isprime function - uber1337 - 04-06-2010
(04-05-2010, 06:15 PM)Fallen Wrote:LOL you really need to stop shortening things lol. Why don't you just use C++ and have a full length program on one line?Code:return False if n in [1, 4, 6, 8, 9, 10] else True
You are aswell
RE: isprime function - symetrik - 04-18-2010
Quote:Code:#!/usr/bin/env python
def isprime(n):
if n > 10:
for x in range(2, 11): if n%x == 0: return False
else: return True
if n <= 10: return False if n in [1, 4, 6, 8, 9, 10] else True
Defeated by:
Code:
if isprime(x) and x > 11: isprime(x**x)For example:
Code:
if isprime(13) and x > 11: # Will return true, as 13 is a prime and is larger than 10.
isprime(13**13) # As 13 is not in the check list, this number will be found to be a prime, even though it clearly is not.RE: isprime function - wat - 05-05-2010
Your function assumes that all composite numbers above 10 are divisible by a number smaller than 10; not true.
Here's an article explaining some of the intricacies that go into finding prime numbers
. Keep in mind that the first method mentioned could be optimized more by only checking numbers smaller than sqrt(num) instead of num / 2.