Very marginal cleanup: startswith usage

[sirosen]

A single startswith call, rather than an or (which will usually not
short-circuit) will make every call to send a request via SDK clients a
little faster.

[derek-globus]

[kurtmckee]

@sirosen If I'm interpreting your narrative text correctly, I need to point out that this is not a speed consideration because .startswith("http://") is not pre-evaluated and then fallen back to as a boolean value. That is, Python doesn't call .startswith() twice and then interpret the or:

return s.startswith("https://") or s.startswith("http://")
     # ^^^^^^^^^^^^^^^^^^^^^^^^    ^^^^^^^^^^^^^^^^^^^^^^^
     # True                        False

return True                     or False

Short-circuiting in Python completely prevents evaluation until it's needed. Thus Python interprets the above in this way:

return s.startswith("https://") or s.startswith("http://")
     # ^^^^^^^^^^^^^^^^^^^^^^^^
     # True

return True

You can see that evaluation of later values is completely suspended until preceding evaluations require it:

print(True  or  (1/0))  # prints 'True'
print(False and (1/0))  # prints 'False'

print(False or  (1/0))  # ZeroDivisionError
print(True  and (1/0))  # ZeroDivisionError

[sirosen]

Indeed! I mostly was here for the stylistic cleanup, and then I noticed -- after the fact -- that the or would be slower when it does not short circuit. I mistakenly declared that it usually doesn't short circuit, but it usually does.
EDIT: that's not quite right, explanation below.

So it's a speedup in a very small set of cases, not the majority case.

---

I reread this again. I see that you're making the point that short-circuiting prevents calls.
That's actually exactly why this is a speed improvement. The original narrative text is fully correct. I've gotten more mixed up in reading your explanation but I was perfectly clear on this at the start.
Both of these startswith() calls evaluate to False in the common case.

So yes, this totally does speed up 99%+ of calls. Not that that's why I did it.