Get memory stats in Pythonista using ctypes

get_available_memory.py

#!/usr/bin/env python3
from ctypes import *
from objc_util import ObjCClass

NSProcessInfo = ObjCClass('NSProcessInfo')
NSByteCountFormatter = ObjCClass('NSByteCountFormatter')

class c_vm_statistics(Structure):
	_fields_ = [('free_count', c_uint),
								('active_count', c_uint),
								('inactive_count', c_uint),
								('wire_count', c_uint),
								('zero_fill_count', c_uint),
								('reactivations', c_uint),
								('pageins', c_uint),
								('pageouts', c_uint),
								('faults', c_uint),
								('cow_faults', c_uint),
								('lookups', c_uint),
								('hits', c_uint),
								('purgeable_count', c_uint),
								('purges', c_uint),
								('speculative_count', c_uint)]

c = cdll.LoadLibrary(None)

mach_host_self = c.mach_host_self
mach_host_self.restype = c_uint
mach_host_self.argtypes = [c_void_p]

host_page_size = c.host_page_size
host_page_size.restype = c_int
host_page_size.argtypes = [c_uint, POINTER(c_uint)]

host_statistics = c.host_statistics
host_statistics.restype = c_int
host_statistics.argtypes = [c_uint, c_int, POINTER(c_int), POINTER(c_uint)]


host_port = c_uint()
host_size = c_uint()
page_size = c_uint()


host_port = mach_host_self(None)
host_size = c_uint(int(sizeof(c_vm_statistics) / sizeof(c_int)))
host_page_size(host_port, byref(page_size))



vm_stat = c_vm_statistics()

HOST_VM_INFO = c_int(2) # This is a c macro
KERN_SUCCESS = 0 # Another c macro (No c_int initializer used because we don't pass it to a c function)

get_host_statistics = host_statistics(host_port, HOST_VM_INFO, cast(byref(vm_stat), POINTER(c_int)), byref(host_size))

if not get_host_statistics == int(KERN_SUCCESS):
	print("Failed to fetch vm statistics")


mem_used = (vm_stat.active_count +
						vm_stat.inactive_count + 
						vm_stat.wire_count) * int(page_size.value)
mem_free = vm_stat.free_count * int(page_size.value)
mem_total = mem_used + mem_free

physical_memory = NSProcessInfo.processInfo().physicalMemory()

byteCountFormtter = NSByteCountFormatter.new()
mem_used = byteCountFormtter.stringFromByteCount_(mem_used)
mem_free = byteCountFormtter.stringFromByteCount_(mem_free)
mem_total = byteCountFormtter.stringFromByteCount_(mem_total)
physical_memory = byteCountFormtter.stringFromByteCount_(physical_memory)

print('used:  ', mem_used)
print('free:  ', mem_free)
print('total: ', mem_total)
print('total (according to Cocoa): ', physical_memory)