The django.core.files module and its submodules contain built-in classes for basic file handling in Django.
The File is a thin wrapper around Python’s built-in file object with some Django-specific additions. Internally, Django uses this class any time it needs to represent a file.
File objects have the following attributes and methods:
The name of file including the relative path from MEDIA_ROOT.
The size of the file in bytes.
The read/write mode for the file.
Open or reopen the file (which by definition also does File.seek(0)). The mode argument allows the same values as Python’s standard open().
When reopening a file, mode will override whatever mode the file was originally opened with; None means to reopen with the original mode.
Read content from the file. The optional size is the number of bytes to read; if not specified, the file will be read to the end.
Iterate over the file yielding one line at a time.
Iterate over the file yielding “chunks” of a given size. chunk_size defaults to 64 KB.
This is especially useful with very large files since it allows them to be streamed off disk and avoids storing the whole file in memory.
Returns True if the file is large enough to require multiple chunks to access all of its content give some chunk_size.
Writes the specified content string to the file. Depending on the storage system behind the scenes, this content might not be fully committed until close() is called on the file.
Close the file.
In addition to the listed methods, File exposes the following attributes and methods of the underlying file object: encoding, fileno, flush, isatty, newlines, read, readinto, readlines, seek, softspace, tell, truncate, writelines, xreadlines.
The ContentFile class inherits from File, but unlike File it operates on string content (bytes also supported), rather than an actual file. For example:
from __future__ import unicode_literals
from django.core.files.base import ContentFile
f1 = ContentFile("esta sentencia está en español")
f2 = ContentFile(b"these are bytes")
Django provides a built-in class specifically for images. django.core.files.images.ImageFile inherits all the attributes and methods of File, and additionally provides the following:
Width of the image in pixels.
Height of the image in pixels.
Any File that’s associated with an object (as with Car.photo, below) will also have a couple of extra methods:
Saves a new file with the file name and contents provided. This will not replace the existing file, but will create a new file and update the object to point to it. If save is True, the model’s save() method will be called once the file is saved. That is, these two lines:
>>> car.photo.save('myphoto.jpg', content, save=False)
>>> car.save()
are the same as this one line:
>>> car.photo.save('myphoto.jpg', content, save=True)
Note that the content argument must be an instance of either File or of a subclass of File, such as ContentFile.
Removes the file from the model instance and deletes the underlying file. If save is True, the model’s save() method will be called once the file is deleted.
Dec 23, 2012