Uploaded Files and Upload Handlers
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 simple wrapper around an uploaded file. You’ll usually use one of these methods to access the uploaded content:
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.
Trueif 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.
A generator returning chunks of the file. If
True, you should use this method in a loop instead of
In practice, it’s often easiest simply 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
The name of the uploaded file (e.g.
The size, in bytes, of the uploaded file.
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.”
A dictionary containing extra parameters passed to the
content-typeheader. 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 section 5.3).
For text/* content-types, the character set (i.e.
utf8) supplied by the browser. Again, “trust but verify” is the best policy here.
Like regular Python files, you can read the file line-by-line simply 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
Previously lines were only split on the Unix end-of-line
A file uploaded into memory (i.e. stream-to-memory). This class is used by the
Built-in upload handlers
TemporaryFileUploadHandler provide Django’s default file upload behavior of reading small files into memory and large ones onto disk. They are located in
File upload handler to stream uploads into memory (used for small files).
Upload handler that streams data into a temporary file using
Writing custom upload handlers
All file upload handlers should be subclasses of
django.core.files.uploadhandler.FileUploadHandler. You can define upload handlers wherever you wish.
Custom file upload handlers must define the following methods:
Receives a “chunk” of data from the file upload.
raw_datais a byte string containing the uploaded data.
startis the position in the file where this
The data you return will get fed into the subsequent upload handlers’
receive_data_chunkmethods. In this way, one handler can be a “filter” for other handlers.
receive_data_chunkto 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
SkipFileexception, the upload will abort or the file will be completely skipped.
Called when a file has finished uploading.
The handler should return an
UploadedFileobject that will be stored in
request.FILES. Handlers may also return
Noneto indicate that the
UploadedFileobject should come from subsequent upload handlers.
Custom upload handlers may also define any of the following optional methods or attributes:
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
For maximum performance the chunk sizes should be divisible by
4and 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_nameis a string name of the file
file_nameis the unicode filename that was provided by the browser.
content_typeis the MIME type provided by the browser – E.g.
content_lengthis the length of the image given by the browser. Sometimes this won’t be provided and will be
charsetis the character set (i.e.
utf8) given by the browser. Like
content_length, this sometimes won’t be provided.
content_type_extrais extra information about the file from the
This method may raise a
StopFutureHandlersexception to prevent future handlers from handling this file.
Callback signaling that the entire upload (all files) has completed.
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_datais a file-like object that supports
METAis the same object as
content_lengthis the length of the data in
input_data. Don’t read more than
boundaryis the MIME boundary for this request.
encodingis the encoding of the request.
Noneif 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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