Running Python Programs under Unix

• UPDATE: On rucs, python is located at /usr/bin/python, not at /usr/local/bin/python, as was originally mentioned below.

Assumptions and notes:

• You are running on rucs2 (I don't know if python is available for the machines in the unix lab
• Assume python is aliased to /usr/local/bin/python
• Assume the file somefile contains this python code:

     i = 3
     print i
  

• Usually we use the extension .py on python program, but this is not required. It is required if you want the code to be a module that can be imported into other python programs and scripts.
• You may want to try the python environment for windows. It's available at www.python.org.

There are several ways to execute a python program:

1. Interactively:

   rucs @ /home/nokie > python
   Python 1.5.1 (#1, Nov 29 1999, 14:33:24)  [GCC 2.8.1] on sunos5
   Copyright 1991-1995 Stichting Mathematisch Centrum, Amsterdam
   >>> i = 5
   >>> print i    
   5
   >>> ^D
   rucs @ /home/nokie > 
   
   

2. Run the interpreter with the file as command line argument:

   rucs @ /home/nokie > python somefile
   3
   rucs @ /home/nokie > 
   

3. Run the interpreter and execute the file:

   rucs @ /home/nokie> python
   Python 1.5.1 (#1, Nov 29 1999, 14:33:24)  [GCC 2.8.1] on sunos5
   Copyright 1991-1995 Stichting Mathematisch Centrum, Amsterdam
   >>> execfile("somefile")        
   3
   

4. Interpret the file directly and go into interpreter (good for debugging):

   rucs @ /home/nokie > python -i somefile
   3
   >>> print i+1
   4
   >>> 
   

5. As a script: Put the line:

    #!/usr/bin/python 

   #!/usr/local/bin/python in as the first line of file afile (starting in column 1), make afile executable, and run afile as a script:

   rucs @ /home/nokie > cat afile
   #!/usr/local/bin/python
   
   #!/usr/local/bin/python
   
   print "This is a script"
   rucs @ /home/nokie > chmod 700 afile 
   rucs @ /home/nokie > afile
   This is a script
   rucs @ /home/nokie > 
   

   To find the current location of python, enter

   which python