pyhdf.HDF | index /usr/lib/python2.4/site-packages/pyhdf/HDF.py

`A module of the pyhdf package implementing the basic API of the
NCSA HDF4 library.
(see: hdf.ncsa.uiuc.edu)
Author: Andre Gosselin
Maurice-Lamontagne Institute
gosselina@dfo-mpo.gc.ca
Version: 0.7-3
Date: July 13 2005
Introduction
------------
The role of the HDF module is to provide support to other modules of the
pyhdf package. It defines constants specifying file opening modes and
various data types, methods for accessing files, plus a few utility
functions to query library version and check if a file is an HDF one.
It should be noted that, among the modules of the pyhdf package, SD is
special in the sense that it is self-contained and does not need support
from the HDF module. For example, SD provides its own file opening and
closing methods, whereas VS uses methods of the HDF.HDF class for that.
Functions and classes summary
-----------------------------
The HDF module provides the following classes.
HC
The HC class holds constants defining opening modes and
various data types.
HDF
The HDF class provides methods to open and close an HDF file,
and return instances of the major HDF APIs (except SD).
To instantiate an HDF class, call the HDF() constructor.
methods:
constructors:
HDF() open an HDF file, creating the file if necessary,
and return an HDF instance
vstart() initialize the VS (Vdata) API over the HDF file and
return a VS instance
vgstart() initialize the V (Vgroup) interface over the HDF file
and return a V instance.
closing file
close() close the HDF file
inquiry
getfileversion() return info about the version of the HDF file
The HDF module also offers the following functions.
inquiry
getlibversion() return info about the version of the library
ishdf() determine whether a file is an HDF file`

Modules
`` |  |
pyhdf.hdfext os | pyhdf sys | types |

Classes
`` |  | __builtin__.object pyhdf.HC.HC HDF exceptions.Exception pyhdf.error.HDF4Error
class HC(__builtin__.object)
`` | `The HC class holds contants defining opening modes and data types. File opening modes (flags ORed together) CREATE 4 create file if it does not exist READ 1 read-only mode TRUNC 256 truncate if it exists WRITE 2 read-write mode Data types CHAR 4 8-bit char CHAR8 4 8-bit char UCHAR 3 unsigned 8-bit integer (0 to 255) UCHAR8 3 unsigned 8-bit integer (0 to 255) INT8 20 signed 8-bit integer (-128 to 127) UINT8 21 unsigned 8-bit integer (0 to 255) INT16 23 signed 16-bit integer UINT16 23 unsigned 16-bit integer INT32 24 signed 32-bit integer UINT32 25 unsigned 32-bit integer FLOAT32 5 32-bit floating point FLOAT64 6 64-bit floating point Tags DFTAG_NDG 720 dataset DFTAG_VH 1962 vdata DFTAG_VG 1965 vgroup`
| Data and other attributes defined here: CHAR = 4 CHAR8 = 4 CREATE = 4 DFTAG_NDG = 720 DFTAG_VG = 1965 DFTAG_VH = 1962 FLOAT32 = 5 FLOAT64 = 6 FULL_INTERLACE = 0 INT16 = 22 INT32 = 24 INT8 = 20 NO_INTERLACE = 1 READ = 1 TRUNC = 256 UCHAR = 3 UCHAR8 = 3 UINT16 = 23 UINT32 = 25 UINT8 = 21 WRITE = 2 __dict__ = <dictproxy object> `dictionary for instance variables (if defined)` __weakref__ = <attribute '__weakref__' of 'HC' objects> `list of weak references to the object (if defined)`
class HDF(__builtin__.object)
`` | `The HDF class encapsulates the basic HDF functions. Its main use is to open and close an HDF file, and return instances of the major HDF APIs (except for SD). To instantiate an HDF class, call the HDF() constructor.`
| Methods defined here: __del__(self) `Delete the instance, first calling the end() method if not already done.` __init__(self, path, mode=1, nblocks=0) `HDF constructor: open an HDF file, creating the file if necessary. Args: path name of the HDF file to open mode file opening mode; this mode is a set of binary flags which can be ored together HC.CREATE combined with HC.WRITE to create file if it does not exist HC.READ open file in read-only access (default) HC.TRUNC if combined with HC.WRITE, overwrite file if it already exists HC.WRITE open file in read-write mode; if file exists it is updated, unless HC.TRUNC is set, in which case it is erased and recreated; if file does not exist, an error is raised unless HC.CREATE is set, in which case the file is created Note an important difference in the way CREATE is handled by the HDF C library and the pyhdf package. In the C library, CREATE indicates that a new file should always be created, overwriting an existing one if any. For pyhdf, CREATE indicates a new file should be created only if it does not exist, and the overwriting of an already existing file must be explicitly asked for by setting the TRUNC flag. Those differences were introduced so as to harmonize the way files are opened in the pycdf and pyhdf packages. Also, this solves a limitation in the hdf (and netCDF) library, where there is no easy way to implement the frequent requirement that an existent file be opened in read-write mode, or created if it does not exist. nblocks number of data descriptor blocks in a block wit which to create the file; the parameter is ignored if the file is not created; 0 asks to use the default Returns: an HDF instance C library equivalent : Hopen` close(self) `Close the HDF file. Args: no argument Returns: None C library equivalent : Hclose` getfileversion(self) `Get file version info. Args: no argument Returns: 4-element tuple with the following components: -major version number (int) -minor version number (int) -complete library version number (int) -additional information (string) C library equivalent : Hgetlibversion` vgstart(self) `Initialize the V API over the file and return a V instance. Args: no argument Returns: V instance C library equivalent : Vstart (in fact: Vinitialize)` vstart(self) `Initialize the VS API over the file and return a VS instance. Args: no argument Returns: VS instance C library equivalent : Vstart (in fact: Vinitialize)` Data and other attributes defined here: __dict__ = <dictproxy object> `dictionary for instance variables (if defined)` __weakref__ = <attribute '__weakref__' of 'HDF' objects> `list of weak references to the object (if defined)`
class HDF4Error(exceptions.Exception)
`` |  | Methods defined here: __init__(self, args=None) Methods inherited from exceptions.Exception: __getitem__(...) __str__(...)

Functions
`` |  | getlibversion() `Get the library version info. Args: no argument Returns: 4-element tuple with the following components: -major version number (int) -minor version number (int) -complete library version number (int) -additional information (string) C library equivalent : Hgetlibversion` ishdf(filename) `Determine whether a file is an HDF file. Args: filename name of the file to check Returns: 1 if the file is an HDF file, 0 otherwise C library equivalent : Hishdf`

Data
`` |  | __all__ = ['HDF', 'HDF4Error', 'HC', 'getlibversion', 'ishdf']