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在Django中流式传输CSV文件
EN

Stack Overflow用户
提问于 2011-03-01 03:22:11
回答 3查看 17.9K关注 0票数 20

我正在尝试将csv文件作为附件下载进行流式传输。CSV文件的大小已经达到4MB或更大,我需要一种让用户主动下载文件的方法,而无需等待所有数据都被创建并提交到内存中。

我首先使用了自己的基于Django的FileWrapper类的文件包装器。但失败了。然后,我在这里看到了一个使用生成器流式传输响应的方法:How to stream an HttpResponse with Django

当我在生成器中引发错误时,我可以看到我使用get_row_data()函数创建了正确的数据,但是当我试图返回响应时,它返回为空。我还禁用了Django GZipMiddleware。有人知道我做错了什么吗?

编辑:我遇到的问题是 ConditionalGetMiddleware**.我不得不替换它,代码在下面的答案中。**

视图如下所示:

代码语言:javascript
复制
from django.views.decorators.http import condition

@condition(etag_func=None)
def csv_view(request, app_label, model_name):
    """ Based on the filters in the query, return a csv file for the given model """

    #Get the model
    model = models.get_model(app_label, model_name)

    #if there are filters in the query
    if request.method == 'GET':
        #if the query is not empty
        if request.META['QUERY_STRING'] != None:
            keyword_arg_dict = {}
            for key, value in request.GET.items():
                #get the query filters
                keyword_arg_dict[str(key)] = str(value)
            #generate a list of row objects, based on the filters
            objects_list = model.objects.filter(**keyword_arg_dict)
        else:
            #get all the model's objects
            objects_list = model.objects.all()
    else:
        #get all the model's objects
        objects_list = model.objects.all()
    #create the reponse object with a csv mimetype
    response = HttpResponse(
        stream_response_generator(model, objects_list),
        mimetype='text/plain',
        )
    response['Content-Disposition'] = "attachment; filename=foo.csv"
    return response

下面是我用来流式传输响应的生成器:

代码语言:javascript
复制
def stream_response_generator(model, objects_list):
    """Streaming function to return data iteratively """
    for row_item in objects_list:
        yield get_row_data(model, row_item)
        time.sleep(1)

下面是我创建csv行数据的方法:

代码语言:javascript
复制
def get_row_data(model, row):
    """Get a row of csv data from an object"""
    #Create a temporary csv handle
    csv_handle = cStringIO.StringIO()
    #create the csv output object
    csv_output = csv.writer(csv_handle)
    value_list = [] 
    for field in model._meta.fields:
        #if the field is a related field (ForeignKey, ManyToMany, OneToOne)
        if isinstance(field, RelatedField):
            #get the related model from the field object
            related_model = field.rel.to
            for key in row.__dict__.keys():
                #find the field in the row that matches the related field
                if key.startswith(field.name):
                    #Get the unicode version of the row in the related model, based on the id
                    try:
                        entry = related_model.objects.get(
                            id__exact=int(row.__dict__[key]),
                            )
                    except:
                        pass
                    else:
                        value = entry.__unicode__().encode("utf-8")
                        break
        #if it isn't a related field
        else:
            #get the value of the field
            if isinstance(row.__dict__[field.name], basestring):
                value = row.__dict__[field.name].encode("utf-8")
            else:
                value = row.__dict__[field.name]
        value_list.append(value)
    #add the row of csv values to the csv file
    csv_output.writerow(value_list)
    #Return the string value of the csv output
    return csv_handle.getvalue()
EN

回答 3

Stack Overflow用户

回答已采纳

发布于 2011-03-01 04:53:59

下面是一些用于流式传输CSV的简单代码;您可能可以从这里开始执行所需的任何操作:

代码语言:javascript
复制
import cStringIO as StringIO
import csv

def csv(request):
    def data():
        for i in xrange(10):
            csvfile = StringIO.StringIO()
            csvwriter = csv.writer(csvfile)
            csvwriter.writerow([i,"a","b","c"])
            yield csvfile.getvalue()

    response = HttpResponse(data(), mimetype="text/csv")
    response["Content-Disposition"] = "attachment; filename=test.csv"
    return response

这只是将每一行写入内存中的文件,读取该行并生成它。

此版本在生成批量数据时效率更高,但在使用它之前,请务必了解以上内容:

代码语言:javascript
复制
import cStringIO as StringIO
import csv

def csv(request):
    csvfile = StringIO.StringIO()
    csvwriter = csv.writer(csvfile)

    def read_and_flush():
        csvfile.seek(0)
        data = csvfile.read()
        csvfile.seek(0)
        csvfile.truncate()
        return data

    def data():
        for i in xrange(10):
            csvwriter.writerow([i,"a","b","c"])
        data = read_and_flush()
        yield data

    response = HttpResponse(data(), mimetype="text/csv")
    response["Content-Disposition"] = "attachment; filename=test.csv"
    return response
票数 34
EN

Stack Overflow用户

发布于 2013-09-27 13:41:01

从Django1.5开始,中间件问题已经得到了解决,并引入了StreamingHttpResponse。执行以下操作:

代码语言:javascript
复制
import cStringIO as StringIO
import csv

def csv_view(request):
    ...
    # Assume `rows` is an iterator or lists
    def stream():
        buffer_ = StringIO.StringIO()
        writer = csv.writer(buffer_)
        for row in rows:
            writer.writerow(row)
            buffer_.seek(0)
            data = buffer_.read()
            buffer_.seek(0)
            buffer_.truncate()
            yield data
    response = StreamingHttpResponse(
        stream(), content_type='text/csv'
    )
    disposition = "attachment; filename=file.csv"
    response['Content-Disposition'] = disposition
    return response

有一些关于how to output csv from Django的文档,但它没有利用StreamingHttpResponse的优势,所以我继续使用opened a ticket in order to track it

票数 11
EN

Stack Overflow用户

发布于 2011-03-03 02:35:03

我遇到的问题是ConditionalGetMiddleware。我看到django-piston为ConditionalGetMiddleware开发了一个支持流媒体的替代中间件:

代码语言:javascript
复制
from django.middleware.http import ConditionalGetMiddleware

def compat_middleware_factory(klass):
    """
    Class wrapper that only executes `process_response`
    if `streaming` is not set on the `HttpResponse` object.
    Django has a bad habbit of looking at the content,
    which will prematurely exhaust the data source if we're
    using generators or buffers.
    """
    class compatwrapper(klass):
        def process_response(self, req, resp):
            if not hasattr(resp, 'streaming'):
                return klass.process_response(self, req, resp)
            return resp
    return compatwrapper

ConditionalMiddlewareCompatProxy = compat_middleware_factory(ConditionalGetMiddleware)

因此,您将用您的ConditionalMiddlewareCompatProxy中间件替换ConditionalGetMiddleware,并且在您的观点中(借用了这个问题的巧妙答案中的代码):

代码语言:javascript
复制
def csv_view(request):
    def data():
        for i in xrange(10):
            csvfile = StringIO.StringIO()
            csvwriter = csv.writer(csvfile)
            csvwriter.writerow([i,"a","b","c"])
            yield csvfile.getvalue()

    #create the reponse object with a csv mimetype
    response = HttpResponse(
        data(),
        mimetype='text/csv',
        )
    #Set the response as an attachment with a filename
    response['Content-Disposition'] = "attachment; filename=test.csv"
    response.streaming = True
    return response
票数 3
EN
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接:

https://stackoverflow.com/questions/5146539

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