Whats the fastes way to delete objects with specific atributes from a list

Question

This is what I have come up with but it feels really clunky and it has to be the slow solution.

class classNameHere(object):
    def __init__(self, number):
        self.value = number

classes = [classNameHere(i) for i in range(1000)]

print(len(classes))

pos = 0

while pos <= len(classes)-1:
    if classes[pos].value % 2:
        del(classes[pos])
    else:
        pos += 1
        
print(len(classes))

This will cause some problems.don't operate the list while iterate it. — jizhihaoSAMA, Jul 26 '20 at 04:39
@jizhihaoSAMA Given that `pos` is only incremented when nothing is removed from the list, then this technically does not cause issues — vallentin, Jul 26 '20 at 04:43
@vallentin In some specific circumstance. If he want to remove some consecutive elements,that will cause this problem. — jizhihaoSAMA, Jul 26 '20 at 04:46

score 0 · Accepted Answer · answered Jul 26 '20 at 04:39

0

You can use a list comprehension:

class classNameHere(object):
    def __init__(self, number):
        self.value = number

classes = [classNameHere(i) for i in range(1000)]
classes = [pos for pos in classes if not pos.value % 2]

print(len(classes))

Output:

answered Jul 26 '20 at 04:39

Red

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OMG that's 100 times nicer. I didn't know you could put if statements into list comprehensions. That opens op so many doors. Are list comprehensions fast? – Jul 26 '20 at 04:46
@TheDopplerEffect, this post should answer you question [`Are list comprehensions fast?`](https://stackoverflow.com/questions/22108488/are-list-comprehensions-and-functional-functions-faster-than-for-loops) – sushanth Jul 26 '20 at 04:56

Whats the fastes way to delete objects with specific atributes from a list

1 Answers1