python newbie

J. Clifford Dyer jcd at sdf.lonestar.org
Fri Nov 2 16:45:45 CET 2007


On Fri, Nov 02, 2007 at 11:13:00AM -0400, Jim Hendricks wrote regarding Re: python newbie:
> 
> BartlebyScrivener wrote:
> > On Nov 2, 8:51 am, Jim Hendricks <j... at bizcomputinginc.com> wrote:
> >> New to python, programming in 15 or so langs for 24 years.
> >>
> >> Couple of questions the tuts I've looked at don't explain:
> > 
> > Did you look at THE tut?  You would seem to be the perfect reader for
> > it, because you are already a programmer.
> > 
> > http://docs.python.org/tut/node6.html#SECTION006600000000000000000
> > 
> > rd
> > 
> 
> I initially looked at THE tut, and it came across so techy that it's 
> such a slow read.  Therefore, I looked to other tuts that were very easy 
> reads and could give me the basic lowdown of the language.  Problem of 
> course is the easy read tuts don't get into the details.
> 
> That said, I looked at the section of the tutorial you provided (thanks) 
> and I am still confused.  It specifies a global var cannot be assigned 
> unless it's specified in the global statement.
> 
> Here's an example of what I am asking:
> 
> def my_function():
>    global x
> 
>    x = open( ....
> 
> before calling my_function, x does not exist in my program.  So, my 
> question is in my_function, the combination of using the global 
> statement, then implicitly creating x via assignment to the result of 
> the open function, is x created in the global namespace?

Yes.

>>> y

Traceback (most recent call last):
  File "<pyshell#8>", line 1, in <module>
    y
NameError: name 'y' is not defined
>>> def f():
		global y
		y = 123
>>> f()
>>> y
123
>>> 

Remember, the interactive interpreter is your friend.  Just type 'python' at the command line and hammer away.  (It's even better through a decent IDE).

Oh yeah, you have to actually call f before y will get defined.  

Cheers,
Cliff



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