django 文件下载

1. 最简单下载:将文件流放入HttpResponse对象即可，适合小文件的下载，但如果这个文件非常大，这种方式会占用大量. 如：

def file_download(request):
# do something...
with open('file_name.txt') as f:
    c = f.read()
return HttpResponse(c)

2. 合理的文件下载

Django的HttpResponse对象允许将迭代器作为传入参数，将上面代码中的传入参数c换成一个迭代器 ，便可以将上述下载功能优化为对大小文件均适合.更加合理的文件下载功能，应该先写一个迭代器，用于处理文件， 然后将这个迭代器作为参数传递给StreaminghttpResponse对象，如：

from django.http import StreamingHttpResponse

def big_file_download(request):
    # do something...

    def file_iterator(file_name, chunk_size=512):
        with open(file_name) as f:
            while True:
                c = f.read(chunk_size)
                if c:
                    yield c
                else:
                    break

    the_file_name = "file_name.txt"
    response = StreamingHttpResponse(file_iterator(the_file_name))

    return response

3.最优文件下载

上述的代码，已经完成了将服务器上的文件，通过文件流传输到浏览器，但文件流通常会以乱码形式显示到浏览器中， 而非下载到硬盘上，因此，还要在做点优化，让文件流写入硬盘。优化很简单，给StreamingHttpResponse对象 的Content-Type和Content-Disposition字段赋下面的值即可，如：

response['Content-Type'] = 'application/octet-stream'
response['Content-Disposition'] = 'attachment;filename="test.pdf"'

完整代码如下:

from django.http import StreamingHttpResponse

def big_file_download(request):
    # do something...

    def file_iterator(file_name, chunk_size=512):
        with open(file_name) as f:
            while True:
                c = f.read(chunk_size)
                if c:
                    yield c
                else:
                    break

    the_file_name = "big_file.pdf"
    response = StreamingHttpResponse(file_iterator(the_file_name))
    response['Content-Type'] = 'application/octet-stream'
    response['Content-Disposition'] = 'attachment;filename="{0}"'.format(the_file_name)

    return response

4.文件名包含中文下载时文件名不对,原因是: url编码解码 ,解决方法如下

from django.utils.http import urlquote

response[‘Content-Disposition‘] = ‘attachment;filename="%s"‘ % (urlquote(title))

5. 遇到的问题：  

下面可以下载成功：

def cmdb_export(request):
    """
    下载文件，发调用写好的 下载文件的 函数总是报错，直接写过来没问题.
    :param request:
    :return:
    """
    if request.method=="GET":
        print("导出ip...........hosts")
        dir_create()
        remove_file("hosts")
        obj = ServerConfInfo.objects.filter(deleted=False)
        for i in obj:
            filename = file_creat(file_name='hosts', mode="a", content=i.ip_net)
            
        response = StreamingHttpResponse(file_iterator(filename))
        response['Content-Type'] = 'application/octet-stream'
        response['Content-Disposition'] = 'attachment;filename="{0}"'.format(filename)
        return response

    else:
        pass

可是改成调用写好的下载函数就报错  didn't return an HttpResponse object. It returned None instead

def cmdb_export(request):
    """
    下载文件，发调用写好的 下载文件的 函数总是报错，直接写过来没问题.
    :param request:
    :return:
    """
    if request.method=="GET":
        print("导出ip...........hosts")
        dir_create()
        remove_file("hosts")
        obj = ServerConfInfo.objects.filter(deleted=False)
        for i in obj:
            filename = file_creat(file_name='hosts', mode="a", content=i.ip_net)

        dj_downloadfile(request,filename)   ##这里调用写好的下载函数。
        # txt = file_iterator(filename)
        # response = StreamingHttpResponse(file_iterator(filename))
        # response['Content-Type'] = 'application/octet-stream'
        # response['Content-Disposition'] = 'attachment;filename="{0}"'.format(filename)
        # return response

    else:
        pass

dj_downloadfile（）函数如下：

def dj_downloadfile(request,filename):
    """
    网页下载数据,发现引用该函数会出现错误，但是把代码拷贝过去是正常的.
    :param request:
    :param filename:
    :return:
    """
    response = StreamingHttpResponse(file_iterator(filename))
    response['Content-Type'] = 'application/octet-stream'
    response['Content-Disposition'] = 'attachment;filename="{0}"'.format(filename)
    return response