I am a beginner in QGIS. I Generally have a doubt: to work in QGIS is it necessary to know Python? whether i am asking we should know to write python programs to make certain modules run?
No you don't need to know Python.
Knowing Python is a good thing however you don't need it to use QGIS. Being able to write and read Python will help you extend it via plugins and scripts if you ever need to.