Crazy question -- Python + Command Line

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Join Date: Apr 2008

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Crazy question -- Python + Command Line

May 21st, 2008

This is probably totally absurd, but...is it possible to, through Python, access the command line and use it? For instance, write a program that outputted all of the files in a given directory, much like

cd [directory]
dir

would?

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Re: Crazy question -- Python + Command Line

May 21st, 2008

indeed it is possible, very easy actually

 Help with Code Tags 
 Python Syntax (Toggle Plain Text) 
import os
os.system("cd [directory]")
import os
os.system("cd [directory]")

and if you want to make it so that you can type commands into your python commandline

 Help with Code Tags 
 Python Syntax (Toggle Plain Text) 
import os
while True:
   command = raw_input("Enter Command->")
   if command.upper() == "Q":
      break
   try:
      os.system(command)
   except:
      print "invalid command\n"
import os
while True:
   command = raw_input("Enter Command->")
   if command.upper() == "Q":
      break
   try:
      os.system(command)
   except:
      print "invalid command\n"

One thing to note is that if you are just going to make specific calls to the command line to do one thing such as cd directory, you should use the python os module rather than just calling the comman shell.

To perform a cd command from python you ould use the following

 Help with Code Tags 
 Python Syntax (Toggle Plain Text) 
import os
os.chdir("C:\\A folder")
import os
os.chdir("C:\\A folder")

This changes the current working directory to C:\Folder. From there you cann call other functions to make directories etc.

Python: os module or type help("os") in the Python command line

you should also look at os.name and os.path especially, help("os.name") etc for information on these.

Hope this helps, just be careful if you do allow user input to access the command prompt.

Chris

Last edited by Freaky_Chris : May 21st, 2008 at 4:20 am.

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Re: Crazy question -- Python + Command Line

May 21st, 2008

That helps very much, thanks! One last thing, is it possible for Python to read the output of the commands it executes? For instance, storing the contents of a directory in a list?

Last edited by FreezeBlink : May 21st, 2008 at 12:45 pm.

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Re: Crazy question -- Python + Command Line

May 21st, 2008

Sorry--I just realized that wasn't worded very clearly. What I mean is this:

Is it possible for Python to store the output of calling os.system([command])? For instance, is it possible to store, in a list, all the results of os.system("dir")?

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Re: Crazy question -- Python + Command Line

May 22nd, 2008

You should look into the os module as i suggested as this allows you to do alot of things. here is an example

 Help with Code Tags 
 Python Syntax (Toggle Plain Text) 
import os
for path, dirs, files in os.walk("C:"):
   print path, dir, files
import os
for path, dirs, files in os.walk("C:"):
   print path, dir, files

ofcourse this is a very basic example and can be expanded greatly. You can loop through files

 Help with Code Tags 
 Python Syntax (Toggle Plain Text) 
for path, dirs, files in os.walk("C:"):
   for f in files:
      print f
for path, dirs, files in os.walk("C:"):
   for f in files:
      print f

so as you can see this way you can do alot of things this way. You can store the files use them to do other things with whatever.

Chris

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Re: Crazy question -- Python + Command Line

May 23rd, 2008

You should indeed use existing/available python modules as you have many built-in functions available for exactly what you need instead of having to sift through output to do something specific. Using python modules instead of calling os-specific commands keeps your programs portable and they perform better.

However, just in case you wish to capture output from external commands, you can use popen:

 Help with Code Tags 
 python Syntax (Toggle Plain Text) 
import os
p = os.popen("dir")
for i in p:
    print i.strip()        # prints the dir output one line at a time
p.close()
import os
p = os.popen("dir")
for i in p:
    print i.strip()        # prints the dir output one line at a time
p.close()