Try... except....Try again?
MRAB
python at mrabarnett.plus.com
Fri Jul 17 15:17:20 CEST 2009
Xavier Ho wrote:
> I have a simple class that generates prime numbers, using memorisation
> and iteration to generate the next prime number.
>
> In the class, I have defined a function that gives, say, the 5th prime
> number. Or the 1000th, it's still very fast. But the code isn't what I
> really like.
>
> def nPrime(self, n):
> "Returns nth prime number, the first one being 2, where n = 0.
> When n = 1, it returns 3."
> while True:
> try:
> return self.primes[n]
> except:
> self.next()
>
> The next() function generates the next prime, and appends it into
> primes. This way, it keeps trying to append until the nth prime
> requested exist, and returns it.
>
> My problem is that it's a "While True" loop, which I get a lot of "Don't
> do it!" In the light of making the code better, what could I do?
>
I wouldn't use a bare "except". What if you had written "prims" instead
of "primes"? It would catch AttributeError and produce the next prime,
repeating until it ran out of memory.
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