• Powerful Python One-Liners

Powerful Python One-Liners

This is a page that is devoted to short programs that can perform powerful operations. The ability to write short programs that are just as powerful as a program written in another lanuage designed to do the same thing. However, it is sometimes fun to try and write a program in Python that is only one line. In other lanugages this would be nearly impossible, but in Python it is a lot easier to do. The trick is to think up something that will "do a lot with a little." I, personally, would love to see this page expanded to the point where it needs some sort of organization system.

Thanks for Your Code, ["JAM"]

Contributed Code

• ["JAM/Code/PlatformFinder"] - This program tells you what platform you are using.
• ["JAM/Code/ComPYiler"] - This program compiles every .py file in the Python directory.
• ["Powerful Python One-Liners/Hostname"] - This programs tells you what your hostname is.

BR Some thoughts by ewo:

• Want to know how much Byte a Terabyte is? If you know further abbreviations you can extend the list.

import pprint;pprint.pprint(zip(('Byte', 'KByte', 'MByte', 'GByte', 'TByte'), [(2**10)**i for i in xrange(5)]))

• And what's the largest number that can be represented by 8 Byte?

import pprint;pprint.pprint(["%i Byte = %i Bit = largest number: %i" %(j, j*8, 256**j) for j in [2**i for i in xrange(8)]])

Cute, isn't it?

Decode a base64 encoded file

import base64, sys; base64.decode(open(sys.argv[1], "rb"), open(sys.argv[2], "wb"))

Editing a list of files in place

I came up with this one-liner in response to an [http://linuxgazette.net/issue96/orr.html article] that said it couldn't be done as an one-liner in Python.

What this does is replace the substring "at" by "op" on all lines of all files (in place) under the path specified (here, the current path).

• Caution: Don't run this on your home directory or you're going to get all your text files edited.

   1 import sys,os,re,fileinput;a=[i[2] for i in os.walk('.') if i[2]] [0];[sys.stdout.write(re.sub('at','op',j)) for j in fileinput(a,inplace=1)]

Craming Python into Makefiles

A related issue is embedding Python into a Makefile. I had a really long script that I was trying to cram into a makefile so I automated the process:

import sys,re

def main():
    fh = open(sys.argv[1],'r')
    lines = fh.readlines()
    print '\tpython2.2 -c "`printf \\"if 1:\\n\\'
    for line in lines:
        re.compile('(?P<char_to_esc>[\\\'\"()])').sub('\\\g<char_to_esc>',line)
        # grab leading white space (should be multiples of 4) and makes them into
        # tabs
        wh_spc_len = len(re.compile('^(?P<lead_white_space>\s*)').search(line).group('lead_white_space'))
        
        sys.stdout.write('\t')
        sys.stdout.write(wh_spc_len/4*'\\t'+line.rstrip().lstrip())
        sys.stdout.write('\\n\\\n')
    print '\t\\"`"'

if __name__=='__main__':
    main()

This script generates a "one-liner" from make's point of view.