I cannot evaluate this statement...

[waltbrad]

The script comes from Mark Lutz's Programming Python. It is the
second line of a script that will launch a python program on any
platform.

import os, sys
pyfile = (sys.platform[:3] == 'win' and 'python.exe') or 'python'

Okay, run on a win32 machine, pyfile evaluates to python.exe

That makes sense. Because the first condition is true and 'python.exe'
is true. So the next comparison is 'python.exe' or 'python' Well,
python.exe is true. So that value is returned to pyfile.

Now. Run this on linux. The first condition evaluates sys.platform[:3]
== 'win' as false. So, the next comparison should be 'False' or
'python' -- This is because 'and' returns the first false value.
But, again, on linux pyfile evaluates to python.exe

Where am I going wrong. And when will this statment make pyfile
evaluate to 'python' ?

[Jerry Hill]

On Fri, Mar 7, 2008 at 3:38 PM, waltbrad <wa******@hotmail.comwrote:

Now. Run this on linux. The first condition evaluates sys.platform[:3]
== 'win' as false. So, the next comparison should be 'False' or
'python' -- This is because 'and' returns the first false value.
But, again, on linux pyfile evaluates to python.exe

This seems to work as expected on my Ubuntu box.

Python 2.5.1 (r251:54863, Oct 5 2007, 13:36:32)
[GCC 4.1.3 20070929 (prerelease) (Ubuntu 4.1.2-16ubuntu2)] on linux2
Type "help", "copyright", "credits" or "license" for more information.

>>import os, sys
sys.platform

'linux2'

>>pyfile = (sys.platform[:3] == 'win' and 'python.exe') or 'python'
pyfile

'python'

>>>

What do you get for sys.platform when you run this code under linux?

--
Jerry

[Steven D'Aprano]

On Fri, 07 Mar 2008 12:38:11 -0800, waltbrad wrote:

The script comes from Mark Lutz's Programming Python. It is the second
line of a script that will launch a python program on any platform.

import os, sys
pyfile = (sys.platform[:3] == 'win' and 'python.exe') or 'python'

Okay, run on a win32 machine, pyfile evaluates to python.exe

That makes sense. Because the first condition is true and 'python.exe'
is true. So the next comparison is 'python.exe' or 'python' Well,
python.exe is true. So that value is returned to pyfile.

Now. Run this on linux. The first condition evaluates sys.platform[:3]
== 'win' as false. So, the next comparison should be 'False' or
'python' -- This is because 'and' returns the first false value. But,
again, on linux pyfile evaluates to python.exe

Not on my Linux box.

>>import os, sys
sys.platform

'linux2'

>>(sys.platform[:3] == 'win' and 'python.exe') or 'python'

'python'

Where am I going wrong. And when will this statment make pyfile
evaluate to 'python' ?

When the first three letters of sys.platform aren't 'win'.


--
Steven