django提供文件下载时，若果文件较小，解决办法是先将要传送的内容全生成在内存中，然后再一次性传入Response对象中：
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def
simple_file_download(request):
# do something...
content
=
open
(
"simplefile"
,
"rb"
).read()
return
HttpResponse(content)
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如果文件非常大时，最简单的办法就是使用静态文件服务器，比如Apache或者Nginx服务器来处理下载。不过有时候，我们需要对用户的权限做一下限定，或者不想向用户暴露文件的真实地址，或者这个大内容是临时生成的(比如临时将多个文件合并而成的)，这时就不能使用静态文件服务器了。
django文档中提到，可以向HttpResponse传递一个迭代器，流式的向客户端传递数据。
要自己写迭代器的话，可以用yield：
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def
read_file(filename, buf_size
=
8192
):
with
open
(filename,
"rb"
) as f:
while
True
:
content
=
f.read(buf_size)
if
content:
yield
content
else
:
break
def
big_file_download(request):
filename
=
"filename"
response
=
HttpResponse(read_file(filename))
return
response
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或者使用生成器表达式，下面是django文档中提供csv大文件下载的例子：
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import
csv
from
django.utils.six.moves
import
range
from
django.http
import
StreamingHttpResponse
class
Echo(
object
):
"""An object that implements just the write method of the file-like
interface.
"""
def
write(
self
, value):
"""Write the value by returning it, instead of storing in a buffer."""
return
value
def
some_streaming_csv_view(request):
"""A view that streams a large CSV file."""
# Generate a sequence of rows. The range is based on the maximum number of
# rows that can be handled by a single sheet in most spreadsheet
# applications.
rows
=
([
"Row {0}"
.
format
(idx),
str
(idx)]
for
idx
in
range
(
65536
))
pseudo_buffer
=
Echo()
writer
=
csv.writer(pseudo_buffer)
response
=
StreamingHttpResponse((writer.writerow(row)
for
row
in
rows),
content_type
=
"text/csv"
)
response[
'Content-Disposition'
]
=
'attachment; filename="somefilename.csv"'
return
response
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python也提供一个文件包装器，将类文件对象包装成一个迭代器：
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class
FileWrapper:
"""Wrapper to convert file-like objects to iterables"""
def
__init__(
self
, filelike, blksize
=
8192
):
self
.filelike
=
filelike
self
.blksize
=
blksize
if
hasattr
(filelike,
'close'
):
self
.close
=
filelike.close
def
__getitem__(
self
,key):
data
=
self
.filelike.read(
self
.blksize)
if
data:
return
data
raise
IndexError
def
__iter__(
self
):
return
self
def
next
(
self
):
data
=
self
.filelike.read(
self
.blksize)
if
data:
return
data
raise
StopIteration
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使用时：
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from
django.core.servers.basehttp
import
FileWrapper
from
django.http
import
HttpResponse
import
os
def
file_download(request,filename):
wrapper
=
FileWrapper(
open
(filename,
'rb'
))
response
=
HttpResponse(wrapper, content_type
=
'application/octet-stream'
)
response[
'Content-Length'
]
=
os.path.getsize(path)
response[
'Content-Disposition'
]
=
'attachment; filename=%s'
%
filename
return
response
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django也提供了StreamingHttpResponse类来代替HttpResponse对流数据进行处理。
压缩为zip文件下载：
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import
os, tempfile, zipfile
from
django.http
import
HttpResponse
from
django.core.servers.basehttp
import
FileWrapper
def
send_zipfile(request):
"""
Create a ZIP file on disk and transmit it in chunks of 8KB,
without loading the whole file into memory. A similar approach can
be used for large dynamic PDF files.
"""
temp
=
tempfile.TemporaryFile()
archive
=
zipfile.ZipFile(temp,
'w'
, zipfile.ZIP_DEFLATED)
for
index
in
range
(
10
):
filename
=
__file__
# Select your files here.
archive.write(filename,
'file%d.txt'
%
index)
archive.close()
wrapper
=
FileWrapper(temp)
response
=
HttpResponse(wrapper, content_type
=
'application/zip'
)
response[
'Content-Disposition'
]
=
'attachment; filename=test.zip'
response[
'Content-Length'
]
=
temp.tell()
temp.seek(
0
)
return
response
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不过不管怎么样，使用django来处理大文件下载都不是一个很好的注意，最好的办法是django做权限判断，然后让静态服务器处理下载。
这需要使用sendfile的机制："传统的Web服务器在处理文件下载的时候，总是先读入文件内容到应用程序内存，然后再把内存当中的内容发送给客户端浏览器。这种方式在应付当今大负载网站会消耗更多的服务器资源。sendfile是现代操作系统支持的一种高性能网络IO方式，操作系统内核的sendfile调用可以将文件内容直接推送到网卡的buffer当中，从而避免了Web服务器读写文件的开销，实现了“零拷贝”模式。 "
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Apache服务器里需要mod_xsendfile模块来实现，而Nginx是通过称为X-Accel-Redirect的特性来实现。
nginx配置文件：
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# Will serve /var/www/files/myfile.tar.gz
# When passed URI /protected_files/myfile.tar.gz
location
/
protected_files {
internal;
alias
/
var
/
www
/
files;
}
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或者
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# Will serve /var/www/protected_files/myfile.tar.gz
# When passed URI /protected_files/myfile.tar.gz
location
/
protected_files {
internal;
root
/
var
/
www;
}
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注意alias和root的区别。
django中：
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response[
'X-Accel-Redirect'
]
=
'/protected_files/%s'
%
filename
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这样当向django view函数发起request时，django负责对用户权限进行判断或者做些其它事情，然后向nginx转发url为/protected_files/filename的请求，nginx服务器负责文件/var/www/protected_files/filename的下载：
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@login_required
def
document_view(request, document_id):
book
=
Book.objects.get(
id
=
document_id)
response
=
HttpResponse()
name
=
book.myBook.name.split(
'/'
)[
-
1
]
response[
'Content_Type'
]
=
'application/octet-stream'
response[
"Content-Disposition"
]
=
"attachment; filename={0}"
.
format
(
name.encode(
'utf-8'
))
response[
'Content-Length'
]
=
os.path.getsize(book.myBook.path)
response[
'X-Accel-Redirect'
]
=
"/protected/{0}"
.
format
(book.myBook.name)
return
response
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