Python Memory Usage: What values are taking up so much memory?

Python seems to use a lot of memory. So what exactly is the overhead of each type of value? Short answer:

int	24
float	24
tuple	63
list	101
dict	298
old-style class	345
new-style class	336
subclassed tuple	79
Record	79
Record with old class mixin	79
Record with new class mixin	79

Measured in bytes using Python 2.5 in 64-bit Ubuntu Linux

I measured these by running a simple program that loaded up 1,000,000 values in a list and then did time.sleep(1000). I ran that for different value types and then ran "top" to see how much memory was being used. I took that value, substracted the memory usage for a list of all the same value (14 bytes each), subtracted the value of a child value (usually an int, 24 bytes each), and then divided by 1,000,000. I'll include the code I ran at the end if you want to cut and paste. So what lessons do we learn from this?

• Python objects are very expensive at over 300 bytes each.
• Tuples have 1/5 as much overhead.
• Records are almost as good as tuples, even when a mixin is added.

So, if you want to have lots of values in memory without using lots of memory, use Record.

If you want to run the test for yourself, here's the code. Just comment out the "make_val" that you want to test.

import time
from Record import Record

class TupleClass(tuple):
    pass

class RecordClass(Record("val")):
    pass

class OldClass:
    def __init__(self, val):
        self.val = val

    def method(self):
        pass

class NewClass(object):
    def __init__(self, val):
        self.val = val

    def method(self):
        pass

class RecordWithOldClass(Record("val"), OldClass):
    pass

class RecordWithNewClass(Record("val"), NewClass):
    pass

make_val = lambda i : 1 #nothing (base overhead)
#make_val = lambda i : i    
#make_val = float           
#make_val = lambda i : (i,) 
#make_val = lambda i : [i]  
#make_val = lambda i : {i:i}
#make_val = TupleClass
#make_val = RecordClass
#make_val = OldClass
#make_val = NewClass
#make_val = RecordWithOldClass
#make_val = RecordWithNewClass

count = 1000000
lst = [make_val(i) for i in xrange(count)]
time.sleep(100000)