Problems using subprocess.call() in Python 2.7.2 on Windows

Question

I\'m trying the following and its failing with an error. I\'ve tried to run it from Python shell/from a script/ on the windows console by invoking python on console. Nothing

Answer 1

pat = "d:\info2.txt"

In Python and most other programming languages, \ is an escape character, which is not included in a string unless doubled. Either use a raw string or escape the escape character:

pat = "d:\\info2.txt"

Answer 2

Escape the \ with \\:

pat = "d:\\info2.txt"

or use "raw" strings:

pat = r"d:\info2.txt"

Answer 3

Add shell=True to call:

>>> import subprocess
>>> subprocess.call('dir', shell=True)
0

As you see, it gives as value the return code, not the output of dir. Also, it waits till the command completes, so doing

>>> subprocess.call('date', shell=True)

will wait for you to enter a new date.

edit: If you want to capture the output, use subprocess.check_output. The DOS command type for example prints out the contents of a file. So, suppose that your file info2.txt contains your username, you would do:

>>> import subprocess
>>> path = r'd:\info2.txt'
>>> output = subprocess.check_output(['type', path], shell=True)
>>> print output
Vinu

For all the ways to call external commands in Python, see this comprehensive overview to a related question, for more about subprocess specifically, see this article by Doug Hellmann.

Answer 4

The 'type' command doesn't run because it's an internal command - internal to the command interpreter/shell called CMD.EXE. You have to call "cmd.exe type filename" instead. The exact code is:

call(['cmd','/C type abc.txt'])