[Python-ideas] string codes & substring equality

[Terry Reedy]

On 11/29/2013 1:40 AM, spir wrote:
> On 11/29/2013 01:45 AM, Steven D'Aprano wrote:
>> Here is my benchmark:
>>
>> py> from timeit import Timer
>> py> setup = "s = 'abcdef'"
>> py> t1 = Timer("ord('c')")  # establish a base-mark of calling ord
>> py> t2 = Timer("ord(s[2])", setup)
>> py> min(t1.repeat(repeat=5))
>> 0.139258101582527
>> py> min(t2.repeat(repeat=5))
>> 0.2207092922180891
>
> You are right, Steven, the benefit is far tinier than I supposed. I
> reproduced this on my machine: the time for char-creation + ord() is
> about 3/2 of ord() alone (which is just indexing).
>
> Now, there is a mystery: how is the time for creating a single-char
> string object about half the time of a simple indexing (in C!)?

Much of the time for ord('c') is the time to make a function call from 
Python. 's[2]' only involves a internal C function call, which is much 
faster.

-- 
Terry Jan Reedy