Limit RAM usage to python program

I'm trying to limit the RAM usage from a Python program to half so it doesn't totally freezes when all the RAM is used, for this I'm using the following code which is not working and my laptop is still freezing:

import sys
import resource

def memory_limit():
    rsrc = resource.RLIMIT_DATA
    soft, hard = resource.getrlimit(rsrc)
    soft /= 2
    resource.setrlimit(rsrc, (soft, hard))

if __name__ == '__main__':
    memory_limit() # Limitates maximun memory usage to half
    try:
        main()
    except MemoryError:
        sys.stderr.write('MAXIMUM MEMORY EXCEEDED')
        sys.exit(-1)

I'm using other functions which I call from the main function.

What am I doing wrong?

Thanks in advance.

PD: I already searched about this and found the code I've put but it's still not working...

I've done some research and found a function to get the memory from Linux systems here: Determine free RAM in Python and I modified it a bit to set the memory hard limit to half of the free memory available.

import resource
import sys

def memory_limit_half():
    """Limit max memory usage to half."""
    soft, hard = resource.getrlimit(resource.RLIMIT_AS)
    # Convert KiB to bytes, and divide in two to half
    resource.setrlimit(resource.RLIMIT_AS, (int(get_memory() * 1024 / 2), hard))

def get_memory():
    with open('/proc/meminfo', 'r') as mem:
        free_memory = 0
        for i in mem:
            sline = i.split()
            if str(sline[0]) in ('MemFree:', 'Buffers:', 'Cached:'):
                free_memory += int(sline[1])
    return free_memory  # KiB

if __name__ == '__main__':
    memory_limit_half()
    try:
        main()
    except MemoryError:
        sys.stderr.write('\n\nERROR: Memory Exception\n')
        sys.exit(1)