CODEWITHSUNDEEP
pythonlistfor-looptimeit
user4016255
user4016255

Reputation:

Slow processing time of a list

Why is my code so sluggish (inefficient)? I need to make two methods to record the time it takes to process a list of a given size. I have a search_fast and search_slow method. Even though there is a difference between those two search times. Search_fast is still pretty slow. I'd like to optimise the processing time so instead of getting 8.99038815498 with search_fast and 65.0739619732 with search_slow. It would only take a fraction of a second. What can I do? I'd be eternally grateful for some tips as coding is still pretty new to me. :)

from timeit import Timer


def fillList(l, n):
    l.extend(range(1, n + 1))
l = []
fillList(l, 100)

def search_fast(l):
    for item in l:
        if item == 10:
            return True
    return False

def search_slow(l):
    return_value = False
    for item in l:
        if item == 10: 
            return_value = True
    return return_value

t = Timer(lambda: search_fast(l))
print t.timeit()
t = Timer(lambda: search_slow(l))
print t.timeit()

Upvotes: 3

Views: 209

Answers (3)

user4016255
user4016255

Reputation:

I managed to find out what made the code sluggish. It was a simple mistake of adding to the list byextend instead of append. 

def fillList(l, n):
    l.**append**(range(1, n + 1))
l = []
fillList(l, 100)

Now search_slowclocks in at 3.91826605797 instead of 65.0739619732. But I have no idea why it changes the performance so much.

Upvotes: 0

MotKohn
MotKohn

Reputation: 3965

Adding the following code to above:

t = Timer(lambda: 10 in l)
print(t.timeit())

produces the following on my system:

0.6166538814701169
3.884095008084452
0.29087270299795875
>>>

Hope this helps. The basic idea is to tap into underlying C code and not make your own Python code.

Upvotes: 1

leovp
leovp

Reputation: 4758

The fastest way is using in operator, which tests membership of a value in a sequence.

if value in some_container:
    …

Reference: https://docs.python.org/3/reference/expressions.html#membership-test-operations

Update: also, if you frequently need to test the membership, consider using sets instead of lists.
Some pros and cons can be found here: https://docs.python.org/3/library/stdtypes.html#set-types-set-frozenset

Upvotes: 1

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