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168 lines
5.6 KiB
Text
168 lines
5.6 KiB
Text
===================
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The ``File`` object
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===================
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The :mod:`django.core.files` module and its submodules contain built-in classes
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for basic file handling in Django.
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.. currentmodule:: django.core.files
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The ``File`` class
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==================
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.. class:: File(file_object)
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The :class:`File` class is a thin wrapper around a Python
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:py:term:`file object` with some Django-specific additions.
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Internally, Django uses this class when it needs to represent a file.
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:class:`File` objects have the following attributes and methods:
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.. attribute:: name
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The name of the file including the relative path from
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:setting:`MEDIA_ROOT`.
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.. attribute:: size
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The size of the file in bytes.
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.. attribute:: file
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The underlying :py:term:`file object` that this class wraps.
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.. admonition:: Be careful with this attribute in subclasses.
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Some subclasses of :class:`File`, including
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:class:`~django.core.files.base.ContentFile` and
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:class:`~django.db.models.fields.files.FieldFile`, may replace this
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attribute with an object other than a Python :py:term:`file object`.
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In these cases, this attribute may itself be a :class:`File`
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subclass (and not necessarily the same subclass). Whenever
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possible, use the attributes and methods of the subclass itself
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rather than the those of the subclass's ``file`` attribute.
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.. attribute:: mode
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The read/write mode for the file.
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.. method:: open(mode=None)
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Open or reopen the file (which also does ``File.seek(0)``).
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The ``mode`` argument allows the same values
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as Python's built-in :func:`python:open()`.
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When reopening a file, ``mode`` will override whatever mode the file
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was originally opened with; ``None`` means to reopen with the original
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mode.
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.. method:: read(num_bytes=None)
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Read content from the file. The optional ``size`` is the number of
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bytes to read; if not specified, the file will be read to the end.
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.. method:: __iter__()
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Iterate over the file yielding one line at a time.
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.. method:: chunks(chunk_size=None)
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Iterate over the file yielding "chunks" of a given size. ``chunk_size``
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defaults to 64 KB.
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This is especially useful with very large files since it allows them to
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be streamed off disk and avoids storing the whole file in memory.
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.. method:: multiple_chunks(chunk_size=None)
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Returns ``True`` if the file is large enough to require multiple chunks
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to access all of its content give some ``chunk_size``.
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.. method:: write(content)
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Writes the specified content string to the file. Depending on the
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storage system behind the scenes, this content might not be fully
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committed until :func:`close()` is called on the file.
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.. method:: close()
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Close the file.
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In addition to the listed methods, :class:`~django.core.files.File` exposes
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the following attributes and methods of its ``file`` object:
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``encoding``, ``fileno``, ``flush``, ``isatty``, ``newlines``,
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``read``, ``readinto``, ``readlines``, ``seek``, ``softspace``, ``tell``,
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``truncate``, ``writelines``, ``xreadlines``, ``readable()``,
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``writable()``, and ``seekable()``.
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.. versionchanged:: 1.11
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The ``readable()`` and ``writable()`` methods were added.
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.. currentmodule:: django.core.files.base
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The ``ContentFile`` class
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=========================
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.. class:: ContentFile(File)
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The ``ContentFile`` class inherits from :class:`~django.core.files.File`,
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but unlike :class:`~django.core.files.File` it operates on string content
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(bytes also supported), rather than an actual file. For example::
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from django.core.files.base import ContentFile
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f1 = ContentFile("esta sentencia está en español")
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f2 = ContentFile(b"these are bytes")
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.. currentmodule:: django.core.files.images
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The ``ImageFile`` class
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=======================
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.. class:: ImageFile(file_object)
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Django provides a built-in class specifically for images.
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:class:`django.core.files.images.ImageFile` inherits all the attributes
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and methods of :class:`~django.core.files.File`, and additionally
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provides the following:
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.. attribute:: width
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Width of the image in pixels.
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.. attribute:: height
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Height of the image in pixels.
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.. currentmodule:: django.core.files
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Additional methods on files attached to objects
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===============================================
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Any :class:`File` that is associated with an object (as with ``Car.photo``,
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below) will also have a couple of extra methods:
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.. method:: File.save(name, content, save=True)
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Saves a new file with the file name and contents provided. This will not
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replace the existing file, but will create a new file and update the object
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to point to it. If ``save`` is ``True``, the model's ``save()`` method will
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be called once the file is saved. That is, these two lines::
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>>> car.photo.save('myphoto.jpg', content, save=False)
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>>> car.save()
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are equivalent to::
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>>> car.photo.save('myphoto.jpg', content, save=True)
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Note that the ``content`` argument must be an instance of either
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:class:`File` or of a subclass of :class:`File`, such as
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:class:`~django.core.files.base.ContentFile`.
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.. method:: File.delete(save=True)
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Removes the file from the model instance and deletes the underlying file.
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If ``save`` is ``True``, the model's ``save()`` method will be called once
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the file is deleted.
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