Link is not working in django

Question

<a href = "{% url 'ngraph' %}">Customer Count</a>

When I click on customer count it works only once and to make it work I have to run the program again, what is the problem here ? And what I have noticed is once the link localhost:8000/graph is (customer count) clicked, works but makes busy to localhost:8000 and doesn't work that link. How to solve it ?

views.py

def graph(request):
    age = ['below 20', '20-22','22-24','24-26','26-28','28-30','30-40','above 40']
    avg_call_group =  [0, 0, 0, 0, 0, 0, 0, 0]

    cursor = connection.cursor()
    cursor.execute("select p.age_group,sum(c.avg_duration) as age_avg_dur from demo p,(select  card_no as card_n, avg(duration) as avg_duration from call_details where service_key = 1 and card_no =calling_no group by card_no) as c where p.card_no = c.card_n group by p.age_group ")
    numrows = int(cursor.rowcount)
    for x in range(numrows):
        row = cursor.fetchone()
        avg_call_group[x] =  row[1]

    cursor.close()

    import matplotlib.pyplot as plt
    f=plt.figure(figsize = (3,3))
    exploding = [.04, .04, .04, .04 , .04, .04, .04, .04]
    age = ['below 20', '20-22','22-24','24-26','26-28','28-30','30-40','40-50']
    plt.pie(avg_call_group, labels= age, autopct='%1.3f%%', explode = exploding)
    canvas = FigureCanvasAgg(f)
    response = HttpResponse(content_type='image/png')
    canvas.print_png(response)
    return response

urls.py

from django.conf.urls import patterns, include, url
from welcome.views import *
from django.contrib import admin
admin.autodiscover()

urlpatterns = patterns('',
    url(r'^admin/', include(admin.site.urls)),
    url(r'^hello/', hello, name = 'nhello'),
    url(r'^graph/', graph, name = 'ngraph'),
)

home.html

<div >
<a href = "{% url 'ngraph' %}">Customer Count</a>
</div>

Alternative source code location: click here

Answer 1

I don't know if you still need an answer but I solved the exact problem like this:

matplotlib.use('Agg') # After you import


# And these lines at the end

fig.clf()
plt.close()
plt.clf()
del var_grid
gc.collect()