Question

I keep having problems with programs in Python (I’m a complete newb) where it doesn’t store the data from a computation and does it over and over again when I feel like it should have saved it. How can I make Python save the answer so it doesn’t compute the program over and over?

ex:

import prime
def g(x):
    i=0
    while i<len(prime.sieve(x)):
        print str(prime.sieve(x)[i])+' is prime'
        i=i+1

Here’s the “prime” module in case someone wants to compile this:

def sieve(max):
    #Takes in a number, and returns all primes between 2 and that number

    #Start with all of the numbers
    primes = range(2,max+1)
    #Start running through each number 
    for i in primes:
            #Start with double the number, and
            j = 2
            #remove all multiples
            while i * j <= primes[-1]:
                    #As long as the current multiple of the number
                    #is less than than the last element in the list
                    #If the multiple is in the list, take it out
                    if i * j in primes:
                            primes.remove(i*j)
                    j=j+1
    return primes

Anyway, the first bit of code computes the list “prime.sieve(x)” over and over, and I want to save it for reference when printing.

Thanks!

rofls

Answer 1

saved_sieve_map = {}
def saved_sieve(x):
  if x not in saved_sieve_map:
    saved_sieve_map[x] = sieve(x)
  return saved_sieve_map[x]