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Groups > comp.lang.python > #43308

Re: performance of script to write very long lines of random chars

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On Thu, Apr 11, 2013 at 11:21 AM, gry <georgeryoung@gmail.com> wrote:
> avail_chrs =
> '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ!"#$%&
> \'()*+,-./:;<=>?@[\\]^_`{}'

Is this exact set of characters a requirement? For instance, would it
be acceptable to instead use this set of characters?

avail_chrs = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'

Your alphabet has 92 characters, this one only 64... the advantage is
that it's really easy to work with a 64-character set; in fact, for
this specific set, it's the standard called Base 64, and Python
already has a module for working with it. All you need is a random
stream of eight-bit characters, which can be provided by os.urandom().

So here's a much simpler version of your program, following the
cut-down character set I offer:

import os
import base64
nchars = 32000000
rows = 10
# Note: If nchars is one higher than a multiple of 4 (eg 5, 9, 101),
# the lines will be one character short (4, 8, 100).
nchars = nchars * 3 // 4
for l in range(rows):
    print(base64.b64encode(os.urandom(nchars)).strip(b'='))


If you can guarantee that your nchars will always be a multiple of 4,
you can drop the .strip() call.

This is going to be *immensely* faster than calling random.choice()
for every character, but it depends on a working os.urandom (it'll
raise NotImplementedError if there's no suitable source). I know it's
available on OS/2, Windows, and Linux, but don't have others handy to
test. If by "a bunch of different computers" you mean exclusively
Linux computers, this should be fine.

ChrisA

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performance of script to write very long lines of random chars gry <georgeryoung@gmail.com> - 2013-04-10 18:21 -0700
  Re: performance of script to write very long lines of random chars Chris Angelico <rosuav@gmail.com> - 2013-04-11 11:45 +1000
    Re: performance of script to write very long lines of random chars Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-04-11 05:33 +0000
      Re: performance of script to write very long lines of random chars Chris Angelico <rosuav@gmail.com> - 2013-04-11 15:53 +1000
  Re: performance of script to write very long lines of random chars Michael Torrie <torriem@gmail.com> - 2013-04-10 19:52 -0600
    Re: performance of script to write very long lines of random chars gry <georgeryoung@gmail.com> - 2013-04-10 19:40 -0700
      Re: performance of script to write very long lines of random chars Chris Angelico <rosuav@gmail.com> - 2013-04-11 13:14 +1000
  Re: performance of script to write very long lines of random chars MRAB <python@mrabarnett.plus.com> - 2013-04-11 04:09 +0100
  Re: performance of script to write very long lines of random chars Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-04-11 07:47 +0000
    Re: performance of script to write very long lines of random chars Oscar Benjamin <oscar.j.benjamin@gmail.com> - 2013-04-11 10:47 +0100
      Re: performance of script to write very long lines of random chars Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-04-11 10:50 +0000
        Re: performance of script to write very long lines of random chars Robert Kern <robert.kern@gmail.com> - 2013-04-11 16:49 +0530
        Re: performance of script to write very long lines of random chars Oscar Benjamin <oscar.j.benjamin@gmail.com> - 2013-04-11 13:05 +0100
        Re: performance of script to write very long lines of random chars Robert Kern <robert.kern@gmail.com> - 2013-04-11 19:06 +0530
        Re: performance of script to write very long lines of random chars Chris Angelico <rosuav@gmail.com> - 2013-04-11 23:56 +1000
  Re: performance of script to write very long lines of random chars Oscar Benjamin <oscar.j.benjamin@gmail.com> - 2013-04-11 10:47 +0100

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