testing python program,project and django site

[Xristos Xristoou]

hello,

i am python user and i have some projects,programs and sites with django
in python.
i want one more step deeper,i want to test my programs for
bugs,weaknesses,vulnerability,security or penetration test,on my sites for crashes(because use python apps).because the user i am now on the feature maybe i have thousand users to work with my programs.
can you tell me how to find this?some propram to do that or some for that ?
some method to do that?
some program to testing the programs?

thnX you