In Python every class can have instance attributes. By default Python uses a dict to store an object’s instance attributes. This is really helpful as it allows setting arbitrary new attributes at runtime.
However, for small classes with known attributes it might be a
bottleneck. The dict wastes a lot of RAM. Python can’t just allocate
a static amount of memory at object creation to store all the
attributes. Therefore it sucks a lot of RAM if you create a lot of
objects (I am talking in thousands and millions). Still there is a way
to circumvent this issue. It involves the usage of __slots__ to
tell Python not to use a dict, and only allocate space for a fixed set
of attributes. Here is an example with and without __slots__:
Without __slots__:
class MyClass(object):
def __init__(name, identifier):
self.name = name
self.identifier = identifier
self.set_up()
# ...With __slots__:
class MyClass(object):
__slots__ = ['name', 'identifier']
def __init__(name, identifier):
self.name = name
self.identifier = identifier
self.set_up()
# ...The second piece of code will reduce the burden on your RAM. Some people have seen almost 40 to 50% reduction in RAM usage by using this technique.
On a sidenote, you might want to give PyPy a try. It does all of these optimizations by default.