# Little novice program written in Python

Rogério Brito rbrito at ime.usp.br
Fri Apr 25 02:31:15 CEST 2008

```Hi, All.

I'm just getting my feet wet on Python and, just for starters, I'm coding some
elementary number theory algorithms (yes, I know that most of them are already
implemented as modules, but this is an exercise in learning the language idioms).

As you can see from the code below, my background is in C, without too much
sophistication.

What I would like is to receive some criticism to my code to make it more
Python'esque and, possibly, use the resources of the computer in a more
efficient way (the algorithm implemented below is the Sieve of Eratosthenes):

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#!/usr/bin/env python

n = int(raw_input())
a = [i for i in range(0,n+1)]
a[1] = 0  # not a prime
prime = 1 # last used prime
finished = False

while (not finished):
prime = prime + 1
# find new prime
while prime*prime <= n and a[prime] == 0:
prime += 1
# cross the composite numbers
if prime*prime <= n:
j = 2*prime
while j <= n:
a[j] = 0
j += prime
else:
finished = True

# print out the prime numbers
i = 2
while i <= n:
if a[i] != 0:
print a[i]
i += 1
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Thank you for any help in improving this program,

--
Rogério Brito : rbrito@{mackenzie,ime.usp}.br : GPG key 1024D/7C2CAEB8
http://www.ime.usp.br/~rbrito : http://meusite.mackenzie.com.br/rbrito
Projects: algorithms.berlios.de : lame.sf.net : vrms.alioth.debian.org

```