Limit Python VM memory

Question

I'm trying to find a way to limit the memory available for the Python VM, as the option "-Xmx" in the Java VM does. (The idea is to be able to play with the MemoryError exception)

I'm not sure this option exist but there may be a solution using a command of the OS to "isolate" a process and its memory.

Thank you.

Answer 1

On *nix you can play around with the ulimit command, specifically the -m (max memory size) and -v (virtual memory).

Answer 2

Don't waste any time on this.

Instead, if you want to play with MemoryError exceptions create a design that isolates object construction so you can test it.

Instead of this

for i in range(1000000000000000000000):
    try:
        y = AnotherClass()
    except MemoryError:
        # the thing we wanted to test

Consider this.

for i in range(1000000000000000000000):
    try:
        y = makeAnotherClass()
    except MemoryError:
        # the thing we wanted to test

This requires one tiny addition to your design.

class AnotherClass( object ):
    def __init__( self, *args, **kw ):
    blah blah blah

def makeAnotherClass( *args, **kw ):
    return AnotherClass( *args, **kw )

The extra function -- in the long run -- proves to be a good design pattern. It's a Factory, and you often need something like it.

You can then replace this makeAnotherClass with something like this.

class Maker( object ):
    def __init__( self, count= 12 ):
        self.count= count
    def __call__( self, *args, **kw ):
        if self.count == 0:
            raise MemoryError
        self.count -= 1
        return AnotherClass( *args, **kw )
 makeAnotherClass= Maker( count=12 )

This version will raise an exception without you having to limit memory in any obscure, unsupportable, complex or magical way.