awips2/pythonPackages/scientific/Scientific/IO/NetCDF.py

# The netCDF interface is mostly written in C; this module only
# adds some luxury and puts everything in its proper place in the
# package hierarchy.
#
# Written by Konrad Hinsen <hinsen@cnrs-orleans.fr>
# Last revision: 2008-8-18
# 

"""
Python interface to the netCDF library
"""

import sys

if sys.modules.has_key('epydoc'):

    # Fake code just for the docstrings!

    from Scientific_netcdf import _C_API

    class NetCDFFile:

        """
        X{netCDF} file

        A NetCDFFile object has two standard attributes: 'dimensions' and
        'variables'. The values of both are dictionaries, mapping dimension
        names to their associated lengths and variable names to variables,
        respectively. Application programs should never modify these
        dictionaries.

        All other attributes correspond to global attributes defined in the
        netCDF file. Global file attributes are created by assigning to
        an attribute of the NetCDFFile object. 
        """

        def __init__(self, filename, mode):
            """
            @param filename: name of the netCDF file. By convention,
                             netCDF files have the extension ".nc", but
                             this is not enforced. The filename may contain
                             a home directory indication starting with "~".
            @type filename: C{str}

            @param mode: access mode. "r" means read-only; no data can be
                         modified. "w" means write; a new file is created,
                         an existing file with the same name is deleted.
                         "a" means append (in analogy with serial files);
                         an existing file is opened for reading and writing,
                         if the file does not exist it is created. "r+" is
                         similar to "a", but the file must already exist.
                         An "s" can be appended to any of the modes listed
                         above; it indicates that the file will be opened
                         or created in "share" mode, which reduces buffering
                         in order to permit simultaneous read access by other
                         processes to a file that is being written.
            @type mode: C{str}
            """
            raise ImportError("this code should never be executed")

        def close(self):
            """
            Close the file. Any read or write access to the file
            or one of its variables after closing raises an exception.
            """
            pass
        
        def createDimension(self, name, length):
            """
            @param name: the name of the dimension
            @type name: C{str}
            @param length: the length of the new dimension. C{None} stands
                           for the unlimited dimension. Note that there
                           can be only one unlimited dimension per file.
            @type length: C{int} or C{NoneType}
            """
            pass

        def createVariable(self, name, type, dimensions):
            """
            @param name: the name of the new variable
            @type name: C{str}
            @param type: the data type of the elements; the same one-letter
                         codes as in C{Numeric} are used and the use of the
                         pre-defined constants (Numeric.Float etc.) is
                         strongly recommended.
            @type type: C{str}
            @param dimensions: a tuple of dimension names that have been
                               defined earlier
            @type dimensions: C{tuple} of C{str}
            @returns: the object corresponding to the new variable
            @rtype: L{NetCDFVariable}
            """
            pass

        def sync(self):
            """
            Write all buffered data to the disk file.
            """
        flush = sync

    class NetCDFVariable:

        """
        Variable in a netCDF file

        NetCDFVariable objects are constructed by calling the method
        'createVariable' on the L{NetCDFFile} object.

        NetCDFVariable objects behave much like array objects defined
        in module Numeric, except that their data resides in a file.
        Data is read by indexing and written by assigning to an
        indexed subset; the entire array can be accessed by the index
        '[:]' or using the methods 'getValue' and
        'assignValue'. NetCDFVariable objects also have attribute
        "shape" with the same meaning as for arrays, but the shape
        cannot be modified. There is another read-only attribute
        "dimensions", whose value is the tuple of dimension names.

        All other attributes correspond to variable attributes defined in the
        netCDF file. Variable attributes are created by assigning to
        an attribute of the NetCDFVariable object. 

        B{Note:}
        If a file open for reading is simultaneously written by another program,
        the size of the unlimited dimension may change. Every time the shape
        of a variable is requested, the current size will be obtained from
        the file. For reading and writing, the size obtained during the last
        shape request is used. This ensures consistency: foo[-1] means the
        same thing no matter how often it is evaluated, as long as the shape
        is not re-evaluated in between.
        """

        def __init__(self, *args):
            raise ImportError("this code should never be executed")

        def assignValue(self, value):
            """
            Assign a new value to the variable. This method allows
            assignment to scalar variables, which cannot be indexed.
            
            @param value: the new value for the variable
            """
            pass

        def getValue(self):
            """
            Return the value of the variable. This method allows
            access to scalar variables, which cannot be indexed.

            @returns: the current value of the variable
            """
            pass

        def typecode(self):
            """
            @returns:  the variable's type code
            @rtype: C{str}
            """
            pass

else:

    # This is the real code.
    from Scientific_netcdf import *
    from Scientific_netcdf import _C_API
    import os

    _NetCDFFile = NetCDFFile
    def NetCDFFile(filename, mode=None, history=None):
        filename = os.path.expanduser(filename)
        args = (filename,)
        if mode is not None:
            args = args + (mode,)
            if history is not None:
                args = args + (history,)
        return apply(_NetCDFFile, args)

    del sys