[Python-ideas] Is this PEP-able? for X in ListY while conditionZ:

[Oscar Benjamin]

On 3 July 2013 06:52, Greg Ewing <greg.ewing at canterbury.ac.nz> wrote:
> Daniel Robinson wrote:
>>
>> That cofactor would have to have a prime factor less than sqrt(n).
>
>
> <facepalm>
> You're right, of course. I feel suitably enfoolished.
> </facepalm>

It took me a little while to understand what you were getting at. My
way of thinking about this is that in every pair of factors either
both are equal to sqrt(n) or one is less than sqrt(n) and the other
greater.

>
> But there is a slight error in the second implementation:
>
>
>     if all(n % p for p in takewhile(lambda p: p**2 < n, primes_seen)):
>
> should be
>
>     if all(n % p for p in takewhile(lambda p: p**2 <= n, primes_seen)):
>
> otherwise it thinks that perfect squares are primes.

Ah, yes. I had it right in the for/while version so I'm going to blame
this typo on takewhile/lambda for obfuscating my code. :)


Oscar