Difference between two 'functions'?

Scripting
,
1

What distinguishes a from b?

a = any(x for x in range(4) if x > 0)
b = any(x > 0 for x in range(4))

print(a)
print(b)
2

Run the list comprehensions separately in a Python REPL and you’ll see.

3 
valuesA = [x for x in range(4) if (x > 0)]
valuesB = [x > 0 for x in range(4)]
print(valuesA)
print(valuesB)
a = any(valuesA)
b = any(valuesB)

print(a)
print(b)

[1, 2, 3]
[False, True, True, True]
True
True
4

Which ‘function’ takes longer to compute between a and b?

5

Spyder code profiler gives b running longer than a.

a = any(x for x in range(4) if x > 0) [800 ns]
b = any(x > 0 for x in range(4)) [1100 ns]

I haven’t run timeit from the command line.

1 Like
6

With a deliberate worst-case scenario:

>>> def case_a():
...     a = [x for x in range(10000) if x>=99999]
...     return any(a)
... 
>>> def case_b():
...     b = [x >= 99999 for x in range(10000)]
...     return any(b)
... 
>>> timeit.timeit(case_b, number=1000)
0.23579104198142886
>>> timeit.timeit(case_a, number=1000)
0.13718337495811284
>>>
2 Likes
7 
9999
????
10000 - 1
8

I purposefully made the test to return False, so the value tested against is larger than the top of the range.

9

ok - i thought you would love to have the last item be the hit …
as you also used >= instead of >

10

I’ve heard that Python is elegant. Is this what they meant to say? :grinning:

print({x for x in range(-100, 100) if any(abs(x**2 - 4) - abs(x**3 / 3) == y for y in range(-100, 100))})