Changing BASH script to Python

Question

I am trying to convert this script to Python but am having problems with the BASH syntax ${variable}. This does something I do not understand as I have very little experience with BASH scripting. My question is basically,how can I do the dollar brackets variable thing in Python ${variable}. In my case the variable is a number from zero to two-hundred and fifty-five. Please see the BASH script below. I am trying to do the exact same thing in Python.

do 
 for code in {0..255}; 
 do echo -e "\e[38;05;${code}m $code: Test"; 
 done; 
done

Here is my attempt to convert the code to a Python script. Unfortunately, I am still having to call BASH via the os.system() method or function. Please check out my script below. The script does not function the same way though, with changing the text in the BASH shell. The Python script below simply prints out the crazy text below and increments the numbers... :/

#! /usr/bin/env python
import os
def run():
 for code in range(0, 255):
 os.system('echo -e "\e[38;05;%dm %s Test"' % (code,str(code)))
run()

Answer 1

You can use print command and string formatting to evaluate your variable during the print.

BTW, you can use xrange rather than range in order not to generate all the numbers in your memory, but to yield it one-by-one (for large range)

You can use this:

import os
def run():
 for code in range(0, 256):
 print "\x1b[38;05;{code}m {code} Test".format(code=code)
run()

• Kijewski: Bash ranges are inclusive: {1..3} = 1 2 3, so you have to increment the upper bound of the range for Python. "\e[38;05;{code}m {code} Test".format(code=code) would be closer to the original (and more readable). Python does not know \e, you need to use \x1b.
• Avihoo Mamka: By fix you mean to use the range() and not xrange() ?
• Avihoo Mamka: Edited my answer. Thanks
• user3808269: In the format method what does "code=code" mean? I am looking at the API and the format method does take several optional arguments but I do not see one named 'code'.
• Avihoo Mamka: That's for replacing the default use of brackets to something more readable and meaningful, so the left side of the assign is the name of the parameter used for the formatting, and the right side of the assign is the actual variable to replace during the formatting. You can use format(foo=code) as well and change in the printing from {code} to {foo}.

Answer 2

You’ll need to use string formatting.

Strangely enough, you already do this in your code (but using the old % syntax instead of the new .format method). I’m not even sure why you think you have to call echo since the string you pass to it is already the string that you are trying to get (if I understand your question right). Just use the print function to output the string.

Answer 3

try this:

#! /usr/bin/env python
import os
def run():
 for code in range(0, 255):
 os.system('/bin/echo -e "\e[38;05;%dm %s Test"' % (code,str(code)))
run()

the echo is usually both extrnal program and internal command of shell, which can make difference sometime

• Kijewski: No, do not try this. You don't need to use external programs for this little example.