http://www.tuicool.com/articles/bUnMfu

django提供檔案下載時，若果檔案較小，解決辦法是先將要傳送的內容全生成在記憶體中，然後再一次性傳入Response物件中：

def simple_file_download(request):
# do something...
content = open("simplefile", "rb").read()
return HttpResponse(content)

如果檔案非常大時，最簡單的辦法就是使用靜態檔案伺服器，比如Apache或者Nginx伺服器來處理下載。不過有時候，我們需要對使用者的許可權做一下限定，或者不想向用戶暴露檔案的真實地址，或者這個大內容是臨時生成的(比如臨時將多個檔案合併而成的)，這時就不能使用靜態檔案伺服器了。

django文件中提到，可以向HttpResponse傳遞一個迭代器，流式的向客戶端傳遞資料。

要自己寫迭代器的話，可以用yield：

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

或者使用生成器表示式，下面是django文件中提供csv大檔案下載的例子：

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

python也提供一個檔案包裝器，將類檔案物件包裝成一個迭代器：

class FileWrapper:
"""Wrapper to convert file-like objects to iterables"""
def __init__(self, filelike, blksize=8192):
self.filelike = filelike
self.blksize = blksize
if 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

使用時：

from django.core.servers.basehttp import FileWrapper
from django.http import HttpResponse
import os
def file_download(request,filename):
wrapper = FileWrapper(file('filepath'))
response = HttpResponse(wrapper, content_type='application/octet-stream')
response['Content-Length'] = os.path.getsize(path)
response['Content-Disposition'] = 'attachment; filename=%s' % filename
return response

django也提供了StreamingHttpResponse類來代替HttpResponse對流資料進行處理。

壓縮為zip檔案下載：

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

不過不管怎麼樣，使用django來處理大檔案下載都不是一個很好的注意，最好的辦法是django做許可權判斷，然後讓靜態伺服器處理下載。

這需要使用sendfile的機制："傳統的Web伺服器在處理檔案下載的時候，總是先讀入檔案內容到應用程式記憶體，然後再把記憶體當中的內容傳送給客戶端瀏覽器。這種方式在應付當今大負載網站會消耗更多的伺服器資源。sendfile是現代作業系統支援的一種高效能網路IO方式，作業系統核心的sendfile呼叫可以將檔案內容直接推送到網絡卡的buffer當中，從而避免了Web伺服器讀寫檔案的開銷，實現了“零拷貝”模式。 "