Generate random perl for http://twitter.com/ThisIsPerl

randomperl.py

#!/usr/bin/python

import os
import random
import shutil
import subprocess
import sys
import tempfile

perl_binary = '/usr/bin/perl'
min_length = 15
max_length = 35
max_tries = 10000
max_to_generate = 50
valid_chars = (['LETTER'] * 3) + (['DIGIT'] * 3) + [
    ' ', '!', '$', '%', '&', '(', ')', '*', '+', ',', '-', '.', '/', ':', ';',
    '<', '=', '>', '?', '@', '[', '\\', ']', '^', '_', '`', '{',  '|',  '}',
    '~', '\n']
valid_letters = [chr(v) for v in range(97, 123)]
valid_digits = [chr(v) for v in range(48, 58)]

dest_file = sys.argv[1] if len(sys.argv) > 1 else ''
FNULL = open(os.devnull, 'w')

with tempfile.NamedTemporaryFile() as tf:
  for i in range(max_tries):
    length = random.randrange(min_length, max_length)
    script = ''
    for _ in range(length):
      script = script + random.choice(valid_chars)

    # Replace LETTER and DIGIT.
    oldscript = ''
    while oldscript != script:
      oldscript = script
      script = script.replace(
        'LETTER', random.choice(valid_letters), 1).replace(
        'DIGIT', random.choice(valid_digits), 1)

    # Filter out:
    # Start with =
    if script[0] == '=':
      continue
    # Start and end with <>
    if script[0] == '<' and script[-1] == '>':
      continue
    # Start and end with the same character (catches `` and ?? and others)
    if script[0] == script[-1]:
      continue

    failed = subprocess.call([perl_binary, '-c', '-e', script],
                              stdout=FNULL, stderr=FNULL)
    if failed == 0:
      if dest_file:
        tf.write(script.replace('\n', '\\n'))
        tf.write('\n')
      else:
        print script.replace('\n', '\\n')
      max_to_generate -= 1
      if max_to_generate == 0:
        sys.exit(0)

  # Copy temp file to sys.argv[1]
  if dest_file:
    tf.flush()
    print 'Copying %s to %s' % (tf.name, dest_file)
    shutil.copy(tf.name, dest_file)
    os.chmod(dest_file, 0644)