Question

Here's my code for PS 1:

what do you think?


from math import *


#problem 1
primes = ()
for n in range(2, 7920):
for i in range(2, n):
if n % i == 0:
break
else:
primes = primes + (n, )

#Problem 2

add = 0
l = 0
for x in range(0,1000):
z = primes [x]
## print z
add += log(z)
print add / primes [x]
## print add, primes [x], add/ primes [x]

Answer 1

Did you try running it? There's no print statement on one. I feel like it's not "finding" the 1000th square root, it's printing out the range which ends on the correct number. I do not have a math background, I'm a philosophy major, so logs are beyond me. I won't try to evaluate your number 2. Haha

Answer 2

pls use a code pasting site - http://dpaste.com/725281/
at line 6 you limited your 'search' range to just above the 1000th prime - which means you already knew what it was - can you change it to be more generic and find the nth prime (in this case n=1000) - i think that was the intent of the problem.

lines 17 and 18 - when you want to iterate over items in a sequence use the 'for item in sequence:' idiom: http://pastebin.com/BMbut2P7
If you need access to the item index and the item use enumerate - http://codepad.org/8x0mERKg

Answer 3

I did this for 1.1: http://dpaste.com/727098/
It seems like an inelegant mess, but it does run.

Answer 4

Erm, I didn't see any instructions or directions for 1.1, besides "write a program that computes and prints the 1000th prime number." All I saw was a list of 'hints,' which I interpreted as being optional to follow. But you're quite right, I did violate some of them (mostly because I didn't really look at them.)

I won't bother posting 1.2 as it turns out to be very easy once 1.1 is done.

Answer 5

line nine: changing a 'for loop' variable inside of the loop can produce unexpected results - it is better to let the for loop increment the variable unless there is a really good reason to do otherwise and you thoroughly understand the consequences.

you are using iter to keep track of how many primes have been found and you are using a for loop to generate possible primes (x). the way you structured it, you have to guess at the range of numbers to generate in order to find 1000 primes - it is best not to write programs that have guess's in them; two bad things can happen, you guess is wrong and you don't get what you want and if you want to use that code for a different prime, you have to guess again. you could probably eliminate the guessing and make it more generic by using a while loop along with iter and another variable that represents the nth prime you are looking for.

iter happens to be a Python builtin function - you shouldn't use variable names that are the same as Python functions.
http://docs.python.org/library/functions.html#iter

Answer 6

bwCA, that's all good reasoning. I rewrote the problem in accordance with it (and just stuck with while loops this time, as they seem to make things less hairy): http://dpaste.com/727426/

I get now why you're not asked to test 2 for primality, it's annoying with while loops. And, yeah, I probably should have figured something was up when iter turned purple... thanks for the list.

Answer 7

line 16 :
http://python.net/~goodger/projects/pycon/2007/idiomatic/handout.html#testing-for-truth-values
http://docs.python.org/library/stdtypes.html#truth-value-testing