Uploaded Files and Upload Handlers

Uploaded files

class UploadedFile

During file uploads, the actual file data is stored in request.FILES. Each entry in this dictionary is an UploadedFile object (or a subclass) – a wrapper around an uploaded file. You’ll usually use one of these methods to access the uploaded content:

UploadedFile.read()

Read the entire uploaded data from the file. Be careful with this method: if the uploaded file is huge it can overwhelm your system if you try to read it into memory. You’ll probably want to use chunks() instead; see below.

UploadedFile.multiple_chunks(chunk_size=None)

Returns True if the uploaded file is big enough to require reading in multiple chunks. By default this will be any file larger than 2.5 megabytes, but that’s configurable; see below.

UploadedFile.chunks(chunk_size=None)

A generator returning chunks of the file. If multiple_chunks() is True, you should use this method in a loop instead of read().

In practice, it’s often easiest to use chunks() all the time. Looping over chunks() instead of using read() ensures that large files don’t overwhelm your system’s memory.

Here are some useful attributes of UploadedFile:

UploadedFile.name

The name of the uploaded file (e.g. my_file.txt).

UploadedFile.size

The size, in bytes, of the uploaded file.

UploadedFile.content_type

The content-type header uploaded with the file (e.g. text/plain or application/pdf). Like any data supplied by the user, you shouldn’t trust that the uploaded file is actually this type. You’ll still need to validate that the file contains the content that the content-type header claims – “trust but verify.”

UploadedFile.content_type_extra

A dictionary containing extra parameters passed to the content-type header. This is typically provided by services, such as Google App Engine, that intercept and handle file uploads on your behalf. As a result your handler may not receive the uploaded file content, but instead a URL or other pointer to the file (see RFC 2388).

UploadedFile.charset

For text/* content-types, the character set (i.e. utf8) supplied by the browser. Again, “trust but verify” is the best policy here.

Note

Like regular Python files, you can read the file line-by-line by iterating over the uploaded file:

for line in uploadedfile:
    do_something_with(line)

Lines are split using universal newlines. The following are recognized as ending a line: the Unix end-of-line convention '\n', the Windows convention '\r\n', and the old Macintosh convention '\r'.

Subclasses of UploadedFile include:

class TemporaryUploadedFile

A file uploaded to a temporary location (i.e. stream-to-disk). This class is used by the TemporaryFileUploadHandler. In addition to the methods from UploadedFile, it has one additional method:

TemporaryUploadedFile.temporary_file_path()

Returns the full path to the temporary uploaded file.

class InMemoryUploadedFile

A file uploaded into memory (i.e. stream-to-memory). This class is used by the MemoryFileUploadHandler.

Built-in upload handlers

Together the MemoryFileUploadHandler and TemporaryFileUploadHandler provide Django’s default file upload behavior of reading small files into memory and large ones onto disk. They are located in django.core.files.uploadhandler.

class MemoryFileUploadHandler

File upload handler to stream uploads into memory (used for small files).

class TemporaryFileUploadHandler

Upload handler that streams data into a temporary file using TemporaryUploadedFile.

Writing custom upload handlers

class FileUploadHandler

All file upload handlers should be subclasses of django.core.files.uploadhandler.FileUploadHandler. You can define upload handlers wherever you wish.

Required methods

Custom file upload handlers must define the following methods:

FileUploadHandler.receive_data_chunk(raw_data, start)

Receives a “chunk” of data from the file upload.

raw_data is a bytestring containing the uploaded data.

start is the position in the file where this raw_data chunk begins.

The data you return will get fed into the subsequent upload handlers’ receive_data_chunk methods. In this way, one handler can be a “filter” for other handlers.

Return None from receive_data_chunk to short-circuit remaining upload handlers from getting this chunk. This is useful if you’re storing the uploaded data yourself and don’t want future handlers to store a copy of the data.

If you raise a StopUpload or a SkipFile exception, the upload will abort or the file will be completely skipped.

FileUploadHandler.file_complete(file_size)

Called when a file has finished uploading.

The handler should return an UploadedFile object that will be stored in request.FILES. Handlers may also return None to indicate that the UploadedFile object should come from subsequent upload handlers.

Optional methods

Custom upload handlers may also define any of the following optional methods or attributes:

FileUploadHandler.chunk_size

Size, in bytes, of the “chunks” Django should store into memory and feed into the handler. That is, this attribute controls the size of chunks fed into FileUploadHandler.receive_data_chunk.

For maximum performance the chunk sizes should be divisible by 4 and should not exceed 2 GB (231 bytes) in size. When there are multiple chunk sizes provided by multiple handlers, Django will use the smallest chunk size defined by any handler.

The default is 64*210 bytes, or 64 KB.

FileUploadHandler.new_file(field_name, file_name, content_type, content_length, charset, content_type_extra)

Callback signaling that a new file upload is starting. This is called before any data has been fed to any upload handlers.

field_name is a string name of the file <input> field.

file_name is the filename provided by the browser.

content_type is the MIME type provided by the browser – E.g. 'image/jpeg'.

content_length is the length of the image given by the browser. Sometimes this won’t be provided and will be None.

charset is the character set (i.e. utf8) given by the browser. Like content_length, this sometimes won’t be provided.

content_type_extra is extra information about the file from the content-type header. See UploadedFile.content_type_extra.

This method may raise a StopFutureHandlers exception to prevent future handlers from handling this file.

FileUploadHandler.upload_complete()

Callback signaling that the entire upload (all files) has completed.

FileUploadHandler.upload_interrupted()

Callback signaling that the upload was interrupted, e.g. when the user closed their browser during file upload.

FileUploadHandler.handle_raw_input(input_data, META, content_length, boundary, encoding)

Allows the handler to completely override the parsing of the raw HTTP input.

input_data is a file-like object that supports read()-ing.

META is the same object as request.META.

content_length is the length of the data in input_data. Don’t read more than content_length bytes from input_data.

boundary is the MIME boundary for this request.

encoding is the encoding of the request.

Return None if you want upload handling to continue, or a tuple of (POST, FILES) if you want to return the new data structures suitable for the request directly.

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