Were you ever in the desperate need to know all primes below 1000?

In Python calculating primes can be done with a one-liner using functional programming concepts lambda function, map(), reduce() and filter():

# Primes <1000
print filter(None,map(lambda y:y*reduce(lambda x,y:x*y!=0,map(lambda x,y=y: y%x, range(2,int(pow(y,0.5)+1))),1), range(2, 1000)))&#91;/sourcecode&#93;

To try this out on a system with python installed in a terminal/console/... type python. In the command prompt showing up paste the line, hit enter and you'll get:
<code>[2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251, 257, 263, 269, 271, 277, 281, 283, 293, 307, 311, 313, 317, 331, 337, 347, 349, 353, 359, 367, 373, 379, 383, 389, 397, 401, 409, 419, 421, 431, 433, 439, 443, 449, 457, 461, 463, 467, 479, 487, 491, 499, 503, 509, 521, 523, 541, 547, 557, 563, 569, 571, 577, 587, 593, 599, 601, 607, 613, 617, 619, 631, 641, 643, 647, 653, 659, 661, 673, 677, 683, 691, 701, 709, 719, 727, 733, 739, 743, 751, 757, 761, 769, 773, 787, 797, 809, 811, 821, 823, 827, 829, 839, 853, 857, 859, 863, 877, 881, 883, 887, 907, 911, 919, 929, 937, 941, 947, 953, 967, 971, 977, 983, 991, 997]</code>Update: Thanks to <a href="http://wordpress.com/blog/2007/09/03/posting-source-code/">Matt</a> and <a href="http://en.forums.wordpress.com/topic.php?id=6435&amp;page&amp;replies=9#post-111641">Mark</a> the code snippet now can look much <a href="http://faq.wordpress.com/2007/09/03/how-do-i-post-source-code/">nicer</a>:


# Primes <1000
print filter(None, map(lambda y: y*reduce(lambda x,y: x*y!=0, map(lambda x,y=y: y%x, range(2, int(pow(y, 0.5)+1))),1),range(2,1000)))&#91;/sourcecode&#93;

Update: Not quite as accurate (compare start of the sequence, 3 is missing) but <a href="http://www.python.org/doc/current/tut/node7.html#SECTION007130000000000000000">much shorter</a> using another formula and filter() and lambda techniques only:


filter(lambda x: x % 2 != 0 and x % 3 != 0, range(2, 1000))

[5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251, 257, 263, 269, 271, 277, 281, 283, 293, 307, 311, 313, 317, 331, 337, 347, 349, 353, 359, 367, 373, 379, 383, 389, 397, 401, 409, 419, 421, 431, 433, 439, 443, 449, 457, 461, 463, 467, 479, 487, 491, 499, 503, 509, 521, 523, 541, 547, 557, 563, 569, 571, 577, 587, 593, 599, 601, 607, 613, 617, 619, 631, 641, 643, 647, 653, 659, 661, 673, 677, 683, 691, 701, 709, 719, 727, 733, 739, 743, 751, 757, 761, 769, 773, 787, 797, 809, 811, 821, 823, 827, 829, 839, 853, 857, 859, 863, 877, 881, 883, 887, 907, 911, 919, 929, 937, 941, 947, 953, 967, 971, 977, 983, 991, 997]

1 Comment

  1. Saturday, 18th Jun 2011 at 13:27

    I’ve learned a few important things via your post. I’d also like to mention that there might be situation in which you will make application for a loan and never need a cosigner such as a U.S. Student Support Loan. However, if you are getting credit through a traditional banker then you need to be able to have a co-signer ready to allow you to. The lenders can base their very own decision on the few aspects but the biggest will be your credit standing. There are some lenders that will furthermore look at your job history and decide based on this but in many cases it will be based on on your credit score.


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