问题
I have a list created with no more than 8 items in it, right now I loop over the item with a standard for loop "for item in list:" I am wondering if there is a way to check all of the elements at the exact same time? I have seen some posts about using zip to iterate over 2 lists at the same time which could help.
If there is no way to iterate over a lists elements at the same time I would guess I need to split one single list into 4 separate lists and iterate 2 at the same time using zip and do the other 2 on a separate thread, that seems like it could be a clunky fix though.
Any help would be appreciated.
Edit Sorry to be vague, I have a list
apples = ['green', 'green', 'green', 'red']
right now I use a for loop to go over each element,
for apple in apples:
checkAppleColour(apple)
#Do some more stuff depending on colour....
right now it loops over each element in apple one by one, what I would like to be able to do is check each of the items at the exact same time for a colour check as every millisecond counts (example code used, but principle is exactly the same for what I am trying to achieve).
Performance is key here I don't mind if its threading I have to use, but I need maximum speed / efficiency for checking each element and my guess is parallelism is the way to do it, I am just not quite sure how.
回答1:
If you can map a function onto the list, parallelism is easy.
def addOne (x):
return x + 1
The default map does things on one thread.
map(addOne, range(1, 4)) #When iterated over produces [2, 3, 4]
If your problem is a map, it means that it's trivially parallel.
from multiprocessing import Pool
pool = Pool()
pool.map(addOne, range(1, 4)) ##When iterated over produces [2, 3, 4]
This uses multiple processes. multiprocessing.dummy.Pool is a thread pool. See this article for a great introduction to the rationale behind both.
来源：https://stackoverflow.com/questions/35319025/python-iterating-over-a-list-in-parallel