import cdms,sys
f=cdms.open(sys.prefix+'/sample_data/clt.nc')

# Query "file" attributes
f.listglobal()
['center', 'comments', 'Conventions', 'model']
print f.Conventions
COARDS

# Now query the file for variables
f.listvariables()
['clt','u','v']

# We can also query for dimensions
f.listdimension()
['plev', 'latitude1', 'latitude2', 'time1', 'longitude1', 'longitude2', 'longitude', 'time', 'latitude', 'plev1', 'time2']

# To query a variable without actually loading it
# in memory first, use a "File Variable" by using []
# Here we create the file variable pointing to 'clt'
# And query it for all available info
V=f['clt']
V.info()
*** Description of Slab clt ***
id: clt
shape: (120, 46, 72)
filename: /lgm/cdat/latest/sample_data/clt.nc
missing_value: None
comments: YONU_AMIP1
grid_name: YONU4X5
grid_type: gaussian
time_statistic: average
long_name: Total cloudiness
units: %
Grid has Python id 0x11dc350.
Gridtype: gaussian
Grid shape: (46, 72)
Order: yx
** Dimension 1 **
 id: time
 Designated a time axis.
 units:  months since 1979-1-1 0
 Length: 120
 First:  0.0
 Last:   119.0
 Python id:  0x11dc5a8
** Dimension 2 **
 id: latitude
 Designated a latitude axis.
 units:  degrees_north
 Length: 46
 First:  -90.0
 Last:   90.0
 Other axis attributes:
 long_name: Latitude
 Python id:  0x11dc698
** Dimension 3 **
 id: longitude
 Designated a longitude axis.
 units:  degrees_east
 Length: 72
 First:  -180.0
 Last:   175.0
 Other axis attributes:
 long_name: Longitude
 Python id:  0x11dc648
*** End of description for clt ***

# This was just a print statement, we can actually
# query the variable for specifics
V.listattributes()
['units', 'time_statistic', 'long_name', 'grid_name', 'comments', 'missing_value', 'grid_type']
V.listdimnames()
['time', 'latitude', 'longitude']

# To query a dimension you can either get it 
# from the file or from the variable
time=f['time']
time.getAxis(0)
time=V.getTime() 
# Time, Level, Latitude, Longitude can be retrieve
# directly independently of where they are in 
# the variable, using getTime, getLevel, getLatitude,
# or getLongitude()