Quickly create a ramdisk in Mac

mkramdisk.py

#!/usr/bin/env python3
# Usage: $0 SIZE
#
# SIZE can be string like "512k", "1G"...

SectorSize = 512                        # Bytes
SIZE_UNITS = {'b': 1.0, 'c': 1.0, 'w': 2.0, 'k': 1024.0,
              'M': 1024.0 * 1024.0, 'G': 1024.0 ** 3.0,
              'T': 1024.0 ** 4.0, 'P': 1024.0 ** 5.0,
              }

def sizeInBytes(size_str):
    """Returns the size in bytes corresponding to `size_str', which is
    something like "2G", "2.5k", etc.  If no unit is specified, byte is assumed.  Valid size units
    are 'b', 'c' (1b), 'w' (2b), 'k', 'M', 'G', 'T', and 'P'.
    """
    Unit = size_str[-1]
    if Unit in SIZE_UNITS:
        Number = float(size_str[:-1])
        return int(Number * SIZE_UNITS[Unit])
    else:
        return int(size_str)

def makeRamDisk(size_in_byte):
    NSectors = int(size_in_byte / SectorSize)
    import subprocess as SubP
    RtVal = SubP.call(\
        'diskutil erasevolume HFS+ "ramdisk" $(hdiutil attach -nomount ram://{})'.format(NSectors),
        shell=True)
    if RtVal != 0:
        raise RuntimeError("Failed to make ram disk...  Diskutil returned {}.".format(RtnVal))

def main(argv):
    if len(argv) != 2:
        print("Usage: {} SIZE".format(argv[0]))
        print()
        print('SIZE can be string like "512k", "1G"...')
        return -1

    Size = argv[1]
    makeRamDisk(sizeInBytes(Size))
    return 0

if __name__ == "__main__":
    import sys
    sys.exit(main(sys.argv))