Simple gist for creating a RAM Disk on Mac OS X (only tested on Yosemite, but it should work on Mavericks, too).

createRamdisk.py

#!/usr/bin/env python3.4

import argparse
import sys
import subprocess

class ErrorToleranteParser(argparse.ArgumentParser):
    def error(self, message):
        sys.stderr.write("error: {}\n".format(message))
        self.print_help()
        sys.exit(2)
        
def isInt(value):
    try:
        int(value)
    except:
        return False
    else:
        return True

def main(size, name="RAM Disk", verbose=False):
    if isInt(size):
        size = int(size)
    else:
        if size[-1] == "g":
            size = int(size[:-1]) * 1024
        else:
            raise ValueError("value needs to be a number or end with g")
    
    command = "diskutil erasevolume HFS+ '{name}' `hdiutil attach -nomount ram://{size}`"
    command = command.format(
        name=name,
        size=size * 2048
    )
    
    if verbose:
        print("Calling: '{}'".format(command))
    
    subprocess.check_call(command, shell=True)
    
if __name__ == "__main__":
    parser = ErrorToleranteParser(
        description='Creates RAM Disks. Proceed with caution. This program has not been tested '
                    'and thus it is probably vulnerable!',
        
    )
    
    parser.add_argument("size", help="The size of the disk in megabytes. Append 'g' if you'd like to user GBs instead.")
    parser.add_argument("--verbose", "-v", action="store_true", help="Verbose, debug output.")
    parser.add_argument("--name", "-n", default="RAM Disk", help="The new of the new RAM Disk.")
    args = parser.parse_args()
    
    code = main(**vars(args))
    try:
        code = int(code)
    except (ValueError, TypeError):
        code = 0
        
    sys.exit(code)