在Django中，在views.py中执行函数时，进入无限循环

Question

I have a function which uses matplotlib and pandas to crunch tweets from txt file and plot a graph.

I'm using that script in views.py in django. It shows the output correctly the first time, however on executing the webpage second time leads to an infinite loop.

I am trying to figure out the reason but can't solve it. Here is the views.py function:

def main():
    print 'Reading Tweets\n'
    tweets_data_path = 'twitter_data.txt'
    tweets_data = []
    tweets_file = open(tweets_data_path, "r")

    for line in tweets_file:
        try:
            tweet = json.loads(line)
            tweets_data.append(tweet)
        except:
            continue

    print 'Structuring Tweets\n'
    tweets = pd.DataFrame()
    tweets['text'] = map(lambda tweet: tweet['text'], tweets_data)
    tweets['lang'] = map(lambda tweet: tweet['lang'], tweets_data)

    print 'Adding programming languages tags to the data\n'

    tweets['python'] = tweets['text'].apply(
        lambda tweet: word_in_text('python', tweet)
    )
    tweets['javascript'] = tweets['text'].apply(
        lambda tweet: word_in_text('javascript', tweet)
    )
    tweets['ruby'] = tweets['text'].apply(
        lambda tweet: word_in_text('ruby', tweet)
    )

    print 'Analyzing tweets by programming language\n'
    prg_langs = ['python', 'javascript', 'ruby']

    tweets_by_prg_lang = [
        tweets['python'].value_counts()[True],
        tweets['javascript'].value_counts()[True], 
        tweets['ruby'].value_counts()[True]
    ]

    x_pos = list(range(len(prg_langs)))
    width = 0.8
    fig, ax = plt.subplots()
    plt.bar(x_pos, tweets_by_prg_lang, width, alpha=1, color='g')
    ax.set_ylabel('Number of tweets', fontsize=15)
    ax.set_title('Ranking:', fontsize=10, fontweight='bold')
    ax.set_xticks([p + 0.4 * width for p in x_pos])
    ax.set_xticklabels(prg_langs)
    plt.grid()
    plt.show()
return render('analytics.html')

This is the url which calls the main function:

 url(r'^analytics/$', 'newsletter.analytics.main', name='analytics'),

It executes in terminal as many times as i want. But stuck in webpages. Please shed some light on me !! PS i am new to Django

Answer 1

Your function needs to take the request as an arg & return a response that can be rendered in the browser.

Then you'll need to decide how to display it, so essentially you'll need to do;

def main(request, *args, **kwargs):
    # all your existing code first, then respond to the request;

    canvas = FigureCanvas(fig)
    response= HttpResponse(mimetype='image/png')
    canvas.print_png(response)
    return response

Then for IE support (some versions ignore content_type ), your URL should specify the image extension;

url(r'^ analytics/simple.png$', 'newsletter. analytics.main'),

If you want it in a popup or similar, maybe you can then look at creating an ajax response. So instead of returning like that, check for if request.is_ajax: then return something like HttpResponse(json_data, mimetype="application/json") .

I've just seen your edit where you've added the return render('analytics.html') . That'll just render the template you've got. You want to pass context with that so that you can display the data you've processed, or just return an image of what you've processed similar to above.