[Python-ideas] Descouraging the implicit string concatenation

[Chris Angelico]

On Thu, Mar 15, 2018 at 12:40 AM, Søren Pilgård <fiskomaten at gmail.com> wrote:
> Of course you can always make error, even in a single letter.
> But I think there is a big difference between mixing up +-/* and **
> where the operator is in "focus" and the implicit concatenation where
> there is no operator.
> A common problem is that you have something like
> foo(["a",
>      "b",
>      "c"
> ]).bar()
> but then you remember that there also needs to be a "d" so you just add
> foo(["a",
>      "b",
>      "c"
>      "d"
> ]).bar()
> Causing an error, not with the "d" expression you are working on but
> due to what you thought was the previous expression but python turns
> it into one.
> The , is seen as a delimiter by the programmer not as part of the
> operation (or the lack of the ,).

You're creating a list. Put a comma at the end of every line; problem
solved. Your edit would be from this:

foo(["a",
    "b",
    "c",
]).bar()

to this:

foo(["a",
    "b",
    "c",
    "d",
]).bar()

and there is no bug. In fact, EVERY time you lay out a list display
vertically (or dict or set or any equivalent), ALWAYS put commas. That
way, you can reorder the lines freely (you don't special-case the last
one), you can append a line without changing the previous one (no
noise in the diff), etc, etc, etc.

ChrisA