Calling a Python code through another Python code

Question

So I have a python code, called say program1.py

To execute it normally I do the following

python program1.py -i input.dat -o output.dat

-i indicates what follows is an input file (in this case input.dat)
-o indicates the name of the output file to be written (in this case output.dat)

I tried to call the program (program1.py) within another python code like this:

os.system('/sw/bin/python2.7 program1.py -i Users/Steve/Desktop/{}   -o  Users/Steve/Desktop/{}'.format(inputFile),.format(outputFile))

This does not seem to work. I know I have to use the OS command but the exact way to format for "-i" and "-o" is puzzling.

Can anyone show me what I am doing wrong?

is the 'Users/Steve/Desktop' a typo? Did you mean to put that at root dir? '/Users/... ? — Erik, Aug 30 '13 at 20:39

score 4 · Answer 1 · answered Aug 30 '13 at 20:35

4

I think,you should import the program1 module into your filename.py and use program1 functions on it

answered Aug 30 '13 at 20:35

Arman_Vasilyan

63
7

2

This is probably the right answer, but you should clarify this. I get the feeling that @SteveGrafton doesn't know about `import` (or that he has a strange reason for ignoring it). – Matt Bryant Aug 30 '13 at 20:52
1

maybe.Or he seeks hard ways or alternative to import – Arman_Vasilyan Aug 30 '13 at 20:53

abarnert · Accepted Answer · 2013-08-30T20:57:09.477

The actual problem in your code is that you're not using format correctly. In fact, as written, it won't even compile:

os.system('/sw/bin/python2.7 program1.py -i Users/Steve/Desktop/{}   -o  Users/Steve/Desktop/{}'.format(inputFile),.format(outputFile))

For the first argument to system, you're trying to format a string with two placeholders and only feeding it one value. Then, for the second argument, you're passing .format(outputFile), which is an error.

You can fix all that by writing:

os.system('/sw/bin/python2.7 program1.py -i Users/Steve/Desktop/{}   -o  Users/Steve/Desktop/{}'.format(inputFile, outputFile))

However, this is a bad way to do things. Usually, you can just trivially rewrite your code to import the functionality into your script and call it. If the only reason you're not doing that is to force a child process, multiprocessing is still usually a better way to do that.

But sometimes you do need to do something like this. In that case, you should still not use os.system. First, to run a new script using the same interpreter as your script, use sys.executable rather than hardcoding it. Second, as the os.system docs or help will tell you, you should almost always be using functions in subprocess instead. So:

subprocess.call([sys.executable, 'program1.py',
                 '-i', 'Users/Steve/Desktop/{}'.format(inputfile),
                 '-o', 'Users/Steve/Desktop/{}'.format(outputfile)])

This takes care of all kinds of problems for you—e.g., you don't have to figure out how to quote the filenames in case they have spaces—and it's safer and more efficient to not use the shell if you don't need it for anything.

However, this still probably won't work for you, unless your current working directory happens to be '/'. If you want to use an absolute path, you have to start it with a /.

While we're at it, it's generally better to use path functions instead of string functions to deal with paths, as in os.path.join('/Users/Steve/Desktop', inputfile).

Even better, you might want to look up the current user's desktop instead of hardcoding that path. The way Apple recommends doing this requires installing pyobjc (which comes built-in with Apple's Python installation, but probably doesn't with the Fink installation you're using instead). But then it's as simple as:

desktop = AppKit.NSSearchPathForDirectoriesInDomains(AppKit.NSDesktopDirectory,
                                                     AppKit.NSUserDomainMask, 
                                                     True)[0]

Calling a Python code through another Python code

2 Answers2