Avoid casting the body to a string when it is already a string

[ale-rt]

No description provided.

[leorochael]

I know I'm late to the game, but I don't see the point of this optimization. Python itself already does this, because str is immutable:

>>> x = "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum."

>>> x is str(x)
True

Do we have any timing results that show that doing an extra isinstance() call is cheaper than letting Python itself do it?

[leorochael]

I suppose one advantage of this is if you have a subclass of str, then it would avoid upcasting it back to str:

>>> class WordCountString(str):
...     def words(self, separator=None):
...         return len(self.split(separator))
...

>>> x = WordCountString("Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.")

>>> isinstance(x, str)
True
>>> x is str(x)
False

But in that case, I suggest to add a unit test to make sure we don't lose this change to the next person who decides to "optimize" this, since timeit shows this "optimization" takes double the amount of time in the case where x is exactly an str instance (IPython syntax below):

>> %%timeit x = "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum."
... 
... y = str(x)
... 
 
38.8 ns ± 3.35 ns per loop (mean ± std. dev. of 7 runs, 10,000,000 loops each)

>>> %%timeit x = "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum."
... 
... if isinstance(x, str):
...   y = str(x)
... else:
...   y = x
... 

72.7 ns ± 2.22 ns per loop (mean ± std. dev. of 7 runs, 10,000,000 loops each)

[leorochael]

Even in the case where we're avoiding the upcast, doing the if ourselves seem to be slower:

>>> %%timeit x = WordCountString("Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.")
... 
... if isinstance(x, str):
...   y = str(x)
... else:
...   y = x
... 
85 ns ± 2.89 ns per loop (mean ± std. dev. of 7 runs, 10,000,000 loops each)

>>> %%timeit x = WordCountString("Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.")
... 
... y = str(x)
... 
... 
54.4 ns ± 0.296 ns per loop (mean ± std. dev. of 7 runs, 10,000,000 loops each)

[ale-rt]

Thanks @leorochael for your insight, I had no clue!
I will revert this one