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Filesystem Interface
====================
It requires a relatively small number of methods to implement a working FS object.
If you are looking to implement a working FS object, derive a class from :py:class:`fs.base.FS` and implement the essential methods (below). Be sure to convert all exceptions to instances of :class:`fs.errors.FSError`.
It may also be worthwhile implementing some of the non-essential methods, as the default implementations may not be optimal. For example, the method :meth:`fs.base.FS.move` is implemented as a file copy followed by a delete, but many filesystems can move a file without copying data.
If the filesystem you are implementing maps paths to the native filesystem, be sure to implement :py:meth:`~fs.base.FS.getsyspath`. Doing so will improve performance, especially when copying / moving files between FS objects.
.. _essential-methods:
Essential Methods
-----------------
The following methods are required for a minimal Filesystem interface:
* :meth:`~fs.base.FS.open` Opens a file for read/writing
* :meth:`~fs.base.FS.isfile` Check wether the path exists and is a file
* :meth:`~fs.base.FS.isdir` Check wether a path exists and is a directory
* :meth:`~fs.base.FS.listdir` List the contents of a directory
* :meth:`~fs.base.FS.makedir` Create a new directory
* :meth:`~fs.base.FS.remove` Remove an existing file
* :meth:`~fs.base.FS.removedir` Remove an existing directory
* :meth:`~fs.base.FS.rename` Atomically rename a file or directory
* :meth:`~fs.base.FS.getinfo` Return information about the path e.g. size, mtime
.. _non-essential-methods:
Non - Essential Methods
-----------------------
The following methods have default implementations in :py:class:`fs.base.FS` and aren't required for a functional FS interface. They may be overriden if an alternative implementation can be supplied:
* :meth:`~fs.base.FS.copy` Copy a file to a new location
* :meth:`~fs.base.FS.copydir` Recursively copy a directory to a new location
* :meth:`~fs.base.FS.desc` Return a short destriptive text regarding a path
* :meth:`~fs.base.FS.exists` Check whether a path exists as file or directory
* :meth:`~fs.base.FS.listdirinfo` Get a directory listing along with the info dict for each entry
* :meth:`~fs.base.FS.ilistdir` Generator version of the listdir method
* :meth:`~fs.base.FS.ilistdirinfo` Generator version of the listdirinfo method
* :meth:`~fs.base.FS.getsyspath` Get a file's name in the local filesystem, if possible
* :meth:`~fs.base.FS.hassyspath` Check if a path maps to a system path (recognised by the OS)
* :meth:`~fs.base.FS.getpathurl` Get an external URL at which the given file can be accessed, if possible
* :meth:`~fs.base.FS.haspathurl` Check if a path maps to an external URL
* :meth:`~fs.base.FS.getmeta` Get the value of a filesystem meta value, if it exists
* :meth:`~fs.base.FS.hasmeta` Check if a filesystem meta value exists
* :meth:`~fs.base.FS.move` Move a file to a new location
* :meth:`~fs.base.FS.movedir` Recursively move a directory to a new location
* :meth:`~fs.base.FS.opendir` Opens a directory and returns an FS object that represents it
* :meth:`~fs.base.FS.safeopen` Like :meth:`~fs.base.FS.open` but returns a :class:`~fs.base.NullFile` if the file could not be opened
* :meth:`~fs.base.FS.settimes` Sets the accessed and modified times of a path
.. _utility-methods:
Utility Methods
---------------
The following members have implementations in :py:class:`fs.base.FS` and will probably never require a non-default implementation, although there is nothing to prevent a derived class from implementing these:
* :meth:`~fs.base.FS.createfile` Create a file with data
* :meth:`~fs.base.FS.getcontents` Returns the contents of a file as a string
* :meth:`~fs.base.FS.setcontents` Sets the contents of a file as a string or file-like object
* :meth:`~fs.base.FS.getsize` Returns the number of bytes used for a given file or directory
* :meth:`~fs.base.FS.isdirempty` Checks if a directory contains no files
* :meth:`~fs.base.FS.makeopendir` Creates a directroy (if it exists) and returns an FS object for that directory
* :meth:`~fs.base.FS.walk` Like `listdir` but descends in to sub-directories
* :meth:`~fs.base.FS.walkfiles` Returns an iterable of file paths in a directory, and its sub-directories
* :meth:`~fs.base.FS.walkdirs` Returns an iterable of paths to sub-directories
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