dynamic names

[Robert Brewer]

Val Bykoski wrote:
> I'm currently in a familiar to many business of filing my tax
> return.  Being a big fan of Python and to make the process 
> less painful, 
> i started by writing my favored schedules A,B,C, and the most favored 
> form 1040 in Python.  Everything was a real fun until i got to the
> very famous motif "add lined Lx to Ly".
> This is my naive (master)piece:
> 
> def sumL(L1,L2):
>    # sum up a range of Ls
>    tot=0.
>    for L in range(L1,L2+1): 
>       #nL=exec("L%s" % L)
>       tot=tot + ("L%s" % L)
>    return tot

Val,

If I were writing the same thing, I would probably stop using a separate
name for L1, L2, etcetera; instead I would put them in a list:

def sum_lines(lines, lowerbound, upperbound):
    tot=0.
    for line in lines[lowerbound:upperbound + 1]: 
        tot += line
    return tot

>>> lines = [3.0, 4.0, 5.0, 6.0, 7.0]
>>> sum_lines(lines, 2, 4)
18.0

Of course, once you've put them in a list, you can just use the builtin
sum() function:

>>> sum(lines[2:5])
18.0

...which saves the extra function definition and call overhead, and
makes your code more readable and more manageable. Hope that helps!


Robert Brewer
MIS
Amor Ministries
fumanchu at amor.org