import numpy as np
import netCDF4 as nc4
import os

def get_used_mem():
    # Quick and dirty memory check with `free`,
    # without having to install e.g. psutil
    return int(os.popen('free -m').readlines()[1].split()[2])

# Create test NetCDF data set
size = 10000000
f    = nc4.Dataset('test.nc', 'w')
dim  = f.createDimension('dim', size)
var  = f.createVariable('var', np.double, dimensions=('dim'))
var[:] = np.random.random(size)
f.close()

# Expected size
mem = size*8/1024**2.

mem0 = get_used_mem()

# Re-open and read NetCDF file
f    = nc4.Dataset('test.nc', 'r')
var2 = f.variables['var'][:]

mem1 = get_used_mem()

# For me this prints: "expected mem = ~76, used=77"
print('expected mem = ~{0:.0f} MB, used = {1:.0f} MB'.format(mem,mem1-mem0))