Hello

I think it's better to use += than list.join() when concating strings.

This is more intuitive than other methods.

Also, I personally think it is not good for one variable to change to another type during runtime.

https://github.com/python/cpython/blob/b26a0db8ea2de3a8a8e4b40e69fc8642c7d7cb68/Lib/asyncio/base_events.py#L826

If you look at the link above, `msg` was a list type at first, in the end 
 become a str type.

Hi Wansoo, using += instead of str.join() is less performant. Concatenating n strings with + will create and allocate n new strings will str.join() will carefully look ahead and allocate the correct amount of memory and do all concatenation at one:


➜  ~ python3 -m timeit -s 's = ""' 'for i in range(1_000_000): s += "foo\n"'
5 loops, best of 5: 107 msec per loop
➜  ~ python3 -m timeit -s 'l = ["foo"]*1_000_000' '"\n".join(l)'
20 loops, best of 5: 9.96 msec per loop


It's a common idiom that you will meet a lot in Python.

Remi is correct.
Closing the issue.

In this particular case the number of concatenations is limited, the resulting string is usually short, and the code is not performance critical (it is the __repr__ implementation). So there is no significant advantage of one way over other, and no way is obviously wrong. In such cases the status quo wins.

Well... to be honest, I'm a little confused. bpo-41244 and this issue are completely opposite. I'm not used to Python community yet because it hasn't been long since I joined it.

You're saying that if a particular method is not dramatically good, we prefer to keep the existing one as it is, right?

Your comment was very helpful to me. Maybe I can learn one by one like this.

Thank you very much.