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：
def simple_file_downloadrequest): # do something... content = open"simplefile", "rb").read) return HttpResponsecontent)
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：
def read_filefilename, buf_size=8192):
with openfilename, "rb") as f:
while True:
content = f.readbuf_size)
if content:
yield content
else:
break
def big_file_downloadrequest):
filename = "filename"
response = HttpResponseread_filefilename))
return response
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：
import csv
from django.utils.six.moves import range
from django.http import StreamingHttpResponse
class Echoobject):
"""An object that implements just the write method of the file-like
interface.
"""
def writeself, value):
"""Write the value by returning it, instead of storing in a buffer."""
return value
def some_streaming_csv_viewrequest):
"""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}".formatidx), stridx)] for idx in range65536))
pseudo_buffer = Echo)
writer = csv.writerpseudo_buffer)
response = StreamingHttpResponsewriter.writerowrow) for row in rows),
content_type="text/csv")
response['Content-Disposition'] = 'attachment; filename="somefilename.csv"'
return response
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：
class FileWrapper:
"""Wrapper to convert file-like objects to iterables"""
def __init__self, filelike, blksize=8192):
self.filelike = filelike
self.blksize = blksize
if hasattrfilelike,'close'):
self.close = filelike.close
def __getitem__self,key):
data = self.filelike.readself.blksize)
if data:
return data
raise IndexError
def __iter__self):
return self
def nextself):
data = self.filelike.readself.blksize)
if data:
return data
raise StopIteration
使用时：
from django.core.servers.basehttp import FileWrapper
from django.http import HttpResponse
import os
def file_downloadrequest,filename):
wrapper = FileWrapperopenfilename, 'rb'))
response = HttpResponsewrapper, content_type='application/octet-stream')
response['Content-Length'] = os.path.getsizepath)
response['Content-Disposition'] = 'attachment; filename=%s' % filename
return response
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：
import os, tempfile, zipfile
from django.http import HttpResponse
from django.core.servers.basehttp import FileWrapper
def send_zipfilerequest):
"""
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.ZipFiletemp, 'w', zipfile.ZIP_DEFLATED)
for index in range10):
filename = __file__ # Select your files here.
archive.writefilename, 'file%d.txt' % index)
archive.close)
wrapper = FileWrappertemp)
response = HttpResponsewrapper, content_type='application/zip')
response['Content-Disposition'] = 'attachment; filename=test.zip'
response['Content-Length'] = temp.tell)
temp.seek0)
return response
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。 “
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：
# Will serve /var/www/files/myfile.tar.gz
# When passed URI /protected_files/myfile.tar.gz
location /protected_files {
internal;
alias /var/www/files;
}
或者
# Will serve /var/www/protected_files/myfile.tar.gz
# When passed URI /protected_files/myfile.tar.gz
location /protected_files {
internal;
root /var/www;
}
注意alias和root的区别。
django中：
response['X-Accel-Redirect']='/protected_files/%s'%filename
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：
@login_required
def document_viewrequest, document_id):
book = Book.objects.getid=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.getsizebook.myBook.path)
response['X-Accel-Redirect'] = "/protected/{0}".formatbook.myBook.name)
return response