Path: csiph.com!fu-berlin.de!uni-berlin.de!not-for-mail
From: Tim Chase <python.list@tim.thechases.com>
Newsgroups: comp.lang.python
Subject: Re: Steve D'Aprano, you're the "master". What's wrong with this concatenation statement?
Date: Sun, 8 May 2016 18:37:38 -0500
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Xref: csiph.com comp.lang.python:108398

While I'm not Steven...

On 2016-05-08 19:10, DFS wrote:
> sSQL =  "line 1\n"
> sSQL += "line 2\n"
> sSQL += "line 3"

If you're only doing it once, it's adequate.

If you're doing it within a loop

  for thing in some_iter():
    s = "line1\n"
    s += "line2\n"
    s += "line3"
    use(s, thing)

it's suboptimal.  Solutions include hoisting it out of the loop:

  s = "line1\n"
  s += "line2\n"
  s += "line3"
  for thing in some_iter():
    use(s, thing)

and just specifying it with a multi-line string (still better off
hoisted out of the loop):

  s = """line1
line2
line3"""
  for thing in some_iter():
    use(s, thing)

If you're accruing in a loop

  s = ""
  for thing in some_iter():
    s += mung(thing)

then that's a bad code-smell (you get quadratic behavior as the
strings are constantly resized), usually better replaced with

  s = "".join(mung(thing) for thing in some_iter())

or build them up as a list, then join the results:

  lst = []
  for thing in some_iter():
    if should_use(thing):
      lst.append(thing)
  s = "\n".join(lst)

-tkc