python attribute class used __slot__

Defined in the class attribute __slot__ attribute field limiting example, in the case of large number of objects can be created to reduce the memory footprint.

The object is to create a large number of memory footprint comparison:

1. Class does not use __slot__

class MySlot:def __init__(self, a, b, c):
        self.a = a
        self.b = b
        self.c = c

@profile()
def main():
    myObj_list = list()
    for i in range(50000):
        myObj = MySlot(i, i, i)
        myObj_list.append(myObj)

Results of the:

Line # Mem usage Increment Line Contents
================================================
401 39.7 MiB 39.7 MiB @profile()
402 def main():
403 39.7 MiB 0.0 MiB myObj_list = list()
404 49.9 MiB 0.0 MiB for i in range(50000):
405 49.9 MiB 0.1 MiB myObj = MySlot(i, i, i)
406 49.9 MiB 0.4 MiB myObj_list.append(myObj)

Take up memory about 10M

 

1. Class used __slot__

class MySlot:
    __slots__ = ('a', 'b', 'c')
    def __init__(self, a, b, c):
        self.a = a
        self.b = b
        self.c = c

@profile()
def main():
    myObj_list = list()
    for i in range(50000):
        myObj = MySlot(i, i, i)
        myObj_list.append(myObj)

Results of the:

Line # Mem usage Increment Line Contents
================================================
401 40.3 MiB 40.3 MiB @profile()
402 def main():
403 40.3 MiB 0.0 MiB myObj_list = list()
404 45.7 MiB 0.0 MiB for i in range(50000):
405 45.7 MiB 0.1 MiB myObj = MySlot(i, i, i)
406 45.7 MiB 0.3 MiB myObj_list.append(myObj)

Memory for about 5M

 

1. Explanation

　　__slot__ limit the property value, add attributes other than __slot__ tuple will complain!

　　__slot__ limitation is to add an instance attribute, a display attribute is not added class!