NLTK(Natural Language Toolkit) is the most popular and widely used python library for doing Natural Language Processing(NLP) or Text Mining.
Python provides several frameworks for developing Graphical User Interface(GUI). Tkinter is one of the easy and simple method of developing GUI in python.
Pytube is one of the great open source project in python which can be used to download Youtube videos directly with few lines of codes that provides robust features. Pytube is the lightweight library that is written completely in Python.
Functional programming is a programming paradigm that treats computation as the evaluation of mathematical functions, avoiding changes of state and mutable data. The main idea of functional programming is "what to solve".