import numpy as np
from Scientific.IO.NetCDF import NetCDFFile


def createFile(FileName,lats,lons):
    # create a file object
    File = NetCDFFile(FileName,'w')
    # Create dimensions and associated variables
    # lat
    File.createDimension('lat',len(lats))
    var = File.createVariable('lat','d',('lat',))
    var.long_name = 'latitude'
    var.units = 'degrees north'
    var[:] = lats
    # lon
    File.createDimension('lon',len(lons))
    var = File.createVariable('lon','d',('lon',))
    var.long_name = 'longitude'
    var.units = 'degrees east'
    var[:] = lons
    # time
    # (this is a "record dimension", meaning it doesn't have predefined)
    File.createDimension('time',None)
    var = File.createVariable('time','d',('time',))
    var.long_name = 'time'
    var.units = ''
    # create a data variable called jim
    # note that the 'd' here means the field is type float
    var = File.createVariable('jim','d',('time','lat','lon'))
    var.long_name = 'James'
    var.units = 'J'
    # return the file object
    return File


# define some lats and lons and create a file
lats = np.arange(181)*1. - 90.
lons = np.arange(360)*1.
File = createFile('jim.nc',lats,lons)

# write some data into the file
nlat = len(lats)
nlon = len(lons)
x = np.zeros((nlat,nlon))*0. # creates a field of shape (nlat,nlon) pre-filled with zeros
                          # multiply by 0. to make sure it has type float
                          # (otherwise it will be integer)
# write as the first time instant
File.variables['jim'][0,:,:] = x[:,:]
File.variables['time'][0] = 1

# write as the 2nd time instant
File.variables['jim'][1,:,:] = x[:,:]+1.
File.variables['time'][1] = 2

# CLOSE THE FILE -- VERY IMPORTANT !!!!
File.close()