List Comprehensions in Python look like the code below
[i**2 for i in range(5) if i%2==0]These tend to be fast enough that we don’t care about what get’s executed when. However let us look at the more complex calculation
[heavy_async_calculation(i) for i in range(5) if heavy_check(i)]In this situation, we might want to be sure that the async_calculation is triggered as soon as it is found. We could play it safe with a for loop
for i in range(10) :
if heavy_check(i):
heavy_async_calculation(i)However we can check the order of operations in the list comprehension easily:
def f(i):
print(f"Check {i}%2")
return i%2==0
[print(i) for i in range(10) if f(i)]creates the output
Check 0%2
0
Check 1%2
Check 2%2
2
Check 3%2
Check 4%2
4
[None, None, None]Confirming that the execution of the print / heavy_async_calculation is done as soon as the check passes