Question

Massive apologies for this embarrassing question—

I’m using my MacBook Pro, running snow leopard, and using Python 2.7.1. Trying to run my first script and all the first pages of all my tutorials are laughing at me:

Let me preface with:

$ whereis python  
/usr/bin/python  
$ which python
/Library/Frameworks/Python.framework/Versions/2.7/bin/python

(Is this my issue?)

I wrote helloworld.py to /users/charles in vim:

$ vim helloworld.py  
#!/usr/bin/python  
# Hello World Python Program  

print "Hello World!";

When trying to run it from terminal:

$ helloworld.py
-bash: helloworld.py: command not found

When trying to run it from python:

$ python
>>> helloworld.py
Traceback (most recent call last):
  File :<stdin>", line 1, in <module>
NameError: name 'helloworld' is not defined

From Dive Into Python (not sure if this is pertinent):

$ python
>>> import sys,os
>>> print 'sys.argv[0] =',sys.argv[0]
sys.argv[0]=
>>> pathname=os.path.dirname(sys.argv[0])
>>> print 'path=',pathname
path=
>>> print 'full path=',os.path.abspath(pathname)
full path= /Users/charles

I’m befuddled! Do I need to alter one of my paths so it finds my script?

I’m absolutely new to programming, I actually just found out that terminal was something you could use.

Thanks!

Answer 1

To turn a Python module or script into a standalone program on a UNIX system you have to do two things:

1.) Make sure you have the “shebang” in the top of your script:

#!/usr/bin/python

2.) Make sure the script file is executable. This is done using the chmod command:

chmod +x /path/to/helloworld.py

/path/to/ being the fully qualified file path to your script. If it’s in the current directory, then you can omit the path.

% ls -l
total 0
drwxr-xr-x  2 jathan jathan   60 2011-04-13 15:28 ./
drwxrwxrwt 12 root   root   6.5K 2011-04-13 15:28 ../
-rw-r--r--  1 jathan jathan    0 2011-04-13 15:28 helloworld.py

It’s in my current directory, so let’s make it executable!

% chmod +x helloworld.py 
% ls -l                 
drwxr-xr-x  2 jathan jathan   60 2011-04-13 15:28 ./
drwxrwxrwt 12 root   root   6.5K 2011-04-13 15:28 ../
-rwxr-xr-x  1 jathan jathan    0 2011-04-13 15:28 helloworld.py*

See the “x”s in the permission bits on the left? You’ve done it! Now we can run it:

% ./helloworld.py   
Hello World!

Lastly, never use semicolons as line-endings in Python. It’s not required and it’s ugly!