dynamically generating function assignent

[Xtian Muirhead]

Bjorn Pettersen <bjorn at roguewave.com> wrote in message
news:51C9F3C392D0D111A15600A0C99E64A9AF5605 at localhost...
> You can do:
>
> fn = eval('func_' + 'a') # look it up in the environment
> fn()
>
> -- bjorn
>
> > -----Original Message-----
> > From: anantk at my-deja.com [mailto:anantk at my-deja.com]
> > Sent: Monday, November 01, 1999 11:19 AM
> > To: python-list at python.org
> > Subject: dynamically generating function assignent
> >
> >
> > Hi,
> >
> >   Here is my problem. I have defined say 12 pairs of functions
> >
> > func_a()
> > parse_func_a()
> >
> > func_b()
> > parse_func_b()
> >  .
> > .
> > func_l()
> > parse_func_l()
> >
> >   A file contains a series of strings which are the names of these
> > functions eg:
> >
> > a
> > c
> > f
> > b
> >
> >   Now for each of these strings I need to call the two functions
> > func_<x>(), and parse_func_<x>(), where <x> is the name of
> > the function
> > that string refers to.
> >
> >   I know you can do something like
> >   call = func_a, and call effectively gets assigned to func_a. My
> > question is how can I generate the RHS of this assignment dynamically?
> > So that all I have to do is
> >
> >   <variable> = <next line in file>
> >   call1 = func_<variable>
> >   call2 = parse_func_<variable>
> >   call1()
> >   call2()
> >
> >   Any help would be appriciated.
> >
> >   Thanks
> >
> > -- Anant

Another way would be to load all the functions into a dictionary.
e.g:

def func_1():
    <blah>

def parse_func_1():
    <blah>

...

functions = {'1':(func_1,parse_func_1),
             'a':(func_a, parse_func_a),
                ...}

Then you could look up call1 and call2:

call1, call2 = functions[valueFromFile]
call1()
call2()

This could be easier to catch cases where the value from the file
doesn't match any of the functions defined. (And I prefer this kind
of static lookup to a dynamic lookup. That's just a bias, I guess.
Suffice it to say that both of these ways are nicer than a whole heap
of elifs. (I guess if you had hundreds of these functions, you wouldn't
want to have to type out all of them in a dictionary (with the
attendant likelihood of making an error).))

Xtian

xtian at regurgitator.zzn.com

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