Fix Python – pandas loc vs. iloc vs. at vs. iat?

Recently began branching out from my safe place (R) into Python and and am a bit confused by the cell localization/selection in Pandas. I’ve read the documentation but I’m struggling to understand the practical implications of the various localization/selection options.
Is there a reason why I should ever use .loc or .iloc over at, and iat or vice….

Fix Python – Which is faster in Python: x**.5 or math.sqrt(x)?

I’ve been wondering this for some time. As the title say, which is faster, the actual function or simply raising to the half power?
UPDATE
This is not a matter of premature optimization. This is simply a question of how the underlying code actually works. What is the theory of how Python code works?
I sent Guido van Rossum an email cause I really ….

Fix Python – Fastest way to get the first object from a queryset in django?

Often I find myself wanting to get the first object from a queryset in Django, or return None if there aren’t any. There are lots of ways to do this which all work. But I’m wondering which is the most performant.
qs = MyModel.objects.filter(blah = blah)
if qs.count() > 0:
return qs[0]
else:
return None

Does this result in two database c….

Fix Python – Why is ‘x’ in (‘x’,) faster than ‘x’ == ‘x’?

>>> timeit.timeit(“‘x’ in (‘x’,)”)
0.04869917374131205
>>> timeit.timeit(“‘x’ == ‘x'”)
0.06144205736110564

Also works for tuples with multiple elements, both versions seem to grow linearly:
>>> timeit.timeit(“‘x’ in (‘x’, ‘y’)”)
0.04866674801541748
>>> timeit.timeit(“‘x’ == ‘x’ or ‘x’ == ‘y'”)
0.06565782838087131
>>> timeit.timeit(“‘x’ in (‘y’, ‘….

Fix Python – Why are some float < integer comparisons four times slower than others?

When comparing floats to integers, some pairs of values take much longer to be evaluated than other values of a similar magnitude.
For example:
>>> import timeit
>>> timeit.timeit(“562949953420000.7 < 562949953421000") # run 1 million times 0.5387085462592742 But if the float or integer is made smaller or larger by a certain amount, the compariso....