The parentheses are there for a reason
2008/3/7, Steven D'Aprano <[EMAIL PROTECTED]>: > > 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 > > -- > http://mail.python.org/mailman/listinfo/python-list >
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