class Storage  
The Storage class provides a standardized API for storing files, along with a set of default behaviors that all other storage systems can inherit or override as necessary.  Note When methods return naive datetime objects, the effective timezone used will be the current value of os.environ['TZ']; note that this is usually set from Django’s TIME_ZONE.   
delete(name)  
Deletes the file referenced by name. If deletion is not supported on the target storage system this will raise NotImplementedError instead. 
  
exists(name)  
Returns True if a file referenced by the given name already exists in the storage system, or False if the name is available for a new file. 
  
get_accessed_time(name)  
Returns a datetime of the last accessed time of the file. For storage systems unable to return the last accessed time this will raise NotImplementedError. If USE_TZ is True, returns an aware datetime, otherwise returns a naive datetime in the local timezone. 
  
get_alternative_name(file_root, file_ext)  
Returns an alternative filename based on the file_root and file_ext parameters, an underscore plus a random 7 character alphanumeric string is appended to the filename before the extension. 
  
get_available_name(name, max_length=None)  
Returns a filename based on the name parameter that’s free and available for new content to be written to on the target storage system. The length of the filename will not exceed max_length, if provided. If a free unique filename cannot be found, a SuspiciousFileOperation exception will be raised. If a file with name already exists, get_alternative_name() is called to obtain an alternative name. 
  
get_created_time(name)  
Returns a datetime of the creation time of the file. For storage systems unable to return the creation time this will raise NotImplementedError. If USE_TZ is True, returns an aware datetime, otherwise returns a naive datetime in the local timezone. 
  
get_modified_time(name)  
Returns a datetime of the last modified time of the file. For storage systems unable to return the last modified time this will raise NotImplementedError. If USE_TZ is True, returns an aware datetime, otherwise returns a naive datetime in the local timezone. 
  
get_valid_name(name)  
Returns a filename based on the name parameter that’s suitable for use on the target storage system. 
  
generate_filename(filename)  
Validates the filename by calling get_valid_name() and returns a filename to be passed to the save() method. The filename argument may include a path as returned by FileField.upload_to. In that case, the path won’t be passed to get_valid_name() but will be prepended back to the resulting name. The default implementation uses os.path operations. Override this method if that’s not appropriate for your storage. 
  
listdir(path)  
Lists the contents of the specified path, returning a 2-tuple of lists; the first item being directories, the second item being files. For storage systems that aren’t able to provide such a listing, this will raise a NotImplementedError instead. 
  
open(name, mode='rb')  
Opens the file given by name. Note that although the returned file is guaranteed to be a File object, it might actually be some subclass. In the case of remote file storage this means that reading/writing could be quite slow, so be warned. 
  
path(name)  
The local filesystem path where the file can be opened using Python’s standard open(). For storage systems that aren’t accessible from the local filesystem, this will raise NotImplementedError instead. 
  
save(name, content, max_length=None)  
Saves a new file using the storage system, preferably with the name specified. If there already exists a file with this name name, the storage system may modify the filename as necessary to get a unique name. The actual name of the stored file will be returned. The max_length argument is passed along to get_available_name(). The content argument must be an instance of django.core.files.File or a file-like object that can be wrapped in File. 
  
size(name)  
Returns the total size, in bytes, of the file referenced by name. For storage systems that aren’t able to return the file size this will raise NotImplementedError instead. 
  
url(name)  
Returns the URL where the contents of the file referenced by name can be accessed. For storage systems that don’t support access by URL this will raise NotImplementedError instead.