Confused: Newbie Function Calls

EW ericwoodworth at gmail.com
Wed Aug 11 18:58:17 CEST 2010


On Aug 11, 12:39 pm, fuglyducky <fuglydu... at gmail.com> wrote:
> On Aug 11, 9:31 am, Pinku Surana <sura... at gmail.com> wrote:
>
>
>
>
>
> > On Aug 11, 12:07 pm, fuglyducky <fuglydu... at gmail.com> wrote:
>
> > > I am a complete newbie to Python (and programming in general) and I
> > > have no idea what I'm missing. Below is a script that I am trying to
> > > work with and I cannot get it to work. When I call the final print
> > > function, nothing prints. However, if I print within the individual
> > > functions, I get the appropriate printout.
>
> > > Am I missing something??? Thanks in advance!!!!
>
> > > ################################################
> > > # Global variable
> > > sample_string = ""
>
> > > def gen_header(sample_string):
> > >     HEADER = """
> > >     mymultilinestringhere
> > >     """
>
> > >     sample_string += HEADER
> > >     return sample_string
>
> > > def gen_nia(sample_string):
> > >     NIA = """
> > >     anothermultilinestringhere
> > >     """
>
> > >     sample_string += NIA
> > >     return sample_string
>
> > > gen_header(sample_string)
> > > gen_nia(sample_string)
>
> > > print(sample_string)
>
> > There are 2 problems with your program.
>
> > (1) If you want to use a global variable in a function, you have to
> > add the line "global sample_string" to the beginning of that
> > function.
>
> > (2) Once you do (1), you will get an error because you've got
> > sample_string as a global and a function parameter. Which one do you
> > want to use in the function? You should change the name of the
> > parameter to "sample" to solve that confusion.
>
> > Here's the result, which works for me:
>
> > sample_string = ""
> > def gen_header(sample):
> >     global sample_string
> >     HEADER = """
> >     mymultilinestringhere
> >     """
> >     sample_string = sample + HEADER
> >     return sample_string
> > def gen_nia(sample):
> >     global sample_string
> >     NIA = """
> >     anothermultilinestringhere
> >     """
> >     sample_string = sample + NIA
> >     return sample_string
> > gen_header(sample_string)
> > gen_nia(sample_string)
> > print(sample_string)
>
> Thanks! That did the trick.
>
> I am a bit confused though. I tried to follow a sample in a book
> (which works) where I didn't have to 1) pass the global variable as a
> parameter into the function, 2) did not have to define the global
> variable within the function. I apologize if this is a super stupid
> question but if it is global, why do I have to pass it into the
> function? Shouldn't the global variable be accessible from anywhere???

If it's a global then you don't have to pass it to the function but
you do have to have the line that says:
global sample_string


Now if you think the example in the book didn't do that and it still
worked then if you post that sample I'm sure somebody can tell you why
it worked.  The book example might be doing something different.



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