[Tutor] mistaken about splitting expressions over lines

[eryksun]

On Tue, Jun 25, 2013 at 10:11 AM, Peter Otten <__peter__ at web.de> wrote:
>
> In older Pythons for ("alpha" "beta") the compiler would merge the two
> strings into one whereas ("alpha" + "beta") would trigger a str.__add__()
> call at runtime. Nowadays the peephole optimiser recognizes ("alpha" +
> "beta") and replaces it with a single string:
>
>>>> import dis
>>>> def f():
> ...     return ("alpha" +
> ... "beta")
> ...
>>>> dis.dis(f)
>   3           0 LOAD_CONST               3 ('alphabeta')
>               3 RETURN_VALUE


Constant folding for binary operations has a length limit of 20 for sequences:

    >>> dis.dis(lambda: '0123456789' + '0123456789' + '0')
      1           0 LOAD_CONST               3 ('0123456789
                                                 0123456789')
                  3 LOAD_CONST               2 ('0')
                  6 BINARY_ADD
                  7 RETURN_VALUE


    >>> dis.dis(lambda: (0,1,2,3,4,5,6,7,8,9) +
    ...                 (0,1,2,3,4,5,6,7,8,9) + (0,))
      2           0 LOAD_CONST              13 ((0, 1, 2, 3, 4,
                                                 5, 6, 7, 8, 9,
                                                 0, 1, 2, 3, 4,
                                                 5, 6, 7, 8, 9))
                  3 LOAD_CONST              14 ((0,))
                  6 BINARY_ADD
                  7 RETURN_VALUE