Parsing functions(?)

[Hans Nowak]

On 9 Dec 99, at 15:32, Paul M wrote:

> Dear Pythoneers,
> 
> I'd like to write a "function recorder" class, something like this:
> 
> class frecorder:
>     def __init__(self):
>         self.flist = []
> 
>     def record(self, fxncall):
>         fxn, arg = **UNKNOWN**(fxncall)
>         self.flist.append((fxn,arg))
> 
> Object of this hypothetical class could then be used to build up a
> record of function calls and arguments which could then be applied all at
> one time, something like the following:
> 
> >>> rec = frecorder()
> >>> rec.record(foo(1))

AFAIK, this will pass the *result* of function call foo(1) to the 
method, which has no way of figuring out which how that value was 
obtained.

> >>> rec.record(bar('string', (t1,t2))
> >>> rec.flist
> [(function foo at XXXX, (1,)), (function bar at XXXX, ('string',
> (t1,t2))]
> >>> for i in rec.flist:
>         apply(i[0], i[1])
> 
> etc....
> 
> I know I could instead define the record method like this:
> 
>     def record(self, fname, fargs):
>         self.flist.append((fname, fargs))
> 
> which would be called like:
>     rec.record(foo, (1,))
> 
> but it doesn't seem as natural as the first example, and besides it
> means that one has to remember to do thinks like specify 1-tuples when the
> function only takes a single argument.

Still, this is the way to go. If you worry about those tuples, try 
this approach instead:

# recorder.py

class frecorder:
    def __init__(self):
        self.flist = []

    def record(self, func, *args):
        self.flist.append(func, args)

def twice(x): return x*2

rec = frecorder()
rec.record(id, twice)  # one arg
rec.record(map, twice, [1,2,3])  # two args
rec.record(hex, 78)
rec.record(locals)	# no args

print rec.flist

for func, args in rec.flist:
    print func, '->', args  # show function and args
    print apply(func, args) # show result

#----end of code------

You can call rec.record with the function as the first argument, 
followed by optional second, third, etc. arguments which are the 
arguments for a call of that function. See the example above.

HTH,

--Hans Nowak (zephyrfalcon at hvision.nl)
Homepage: http://fly.to/zephyrfalcon
You call me a masterless man. You are wrong. I am my own master.