Pythonic style

[Tim Chase]

On 2020-09-21 09:48, Stavros Macrakis wrote:
>>   def fn(iterable):
>>     x, = iterable
>>     return x
>
> Thanks, Tim! I didn't realize that you could write (x,) on the LHS!
> Very nice, very Pythonic!

It also expands nicely for other cases, so you want the 3-and-only-3
first values with errors for too many or too few?

  x, y, z = iterable
  x, y, z = (1, 2, 3)

The (x,) version is just the single case.  And it's fast—a single
Python UNPACK_SEQUENCE opcode

  >>> dis.dis(fn)
  2           0 LOAD_FAST                0 (i)
              2 UNPACK_SEQUENCE          1
              4 STORE_FAST               1 (x)

  3           6 LOAD_FAST                1 (x)
              8 RETURN_VALUE

Though now I'm wondering if there's a way to skip the
STORE_FAST/LOAD_FAST instructions and create a function that
generates the opcode sequence

  UNPACK_SEQUENCE 1
  RETURN_VALUE

:-)

(totally tangential ramblings)

-tkc