[Python-ideas] if expensive_computation() as x:

[Terry Reedy]

On 2/13/2014 4:59 PM, Ram Rachum wrote:
> Hi everybody,
>
> Please excuse the recent torrent of crazy ideas :)
>
> I was reading code of the Shpaml project, trying to make a patch, while
> I saw code that looked inelegant to me. I considered how to improve it,
> but then saw I don't know how to.
>
> The code paraphrased is this:
>
>      if expensive_computation_0():
>          x = expensive_computation_0()
>          # Do something with x...
>      elif expensive_computation_1():
>          x = expensive_computation_1()
>          # Do something with x...
>      elif expensive_computation_2():
>          x = expensive_computation_2()
>          # Do something with x...

I do not really understand the fear of indents that would cause one to 
repeat calculations rather than write the actual logic.

     x = expensive_computation_0():
     if x:
         # Do something with x...
     else:
         x = expensive_computation_1()
         if x:
             # Do something with x...
         else:
             x = expensive_computation_2()
             # Do something with x...

If the code is already indented so much that 8 more spaces is a burden, 
then temporarily use 1 space indents. If do_something is the same, I 
would use 'or' as already posted. Python 'or' expressions are 
flow-control expression, not just logic expresssion. If there are more 
nested clauses, a separate function or "while 'fake loop': ... break" is 
fine.

-- 
Terry Jan Reedy