Week 3 Object-Oriented Programming

from my understanding and point of view, Object-Oriented Programming is class. Creating a class is like giving a object some properties that defining by yourself. But there are still some questions in my head. First, i don't understand what __init__ for. Is it the basic properties of that class? Is it possible for a class without __init__?  But, the tutorial work is ok for me, I can finish them very easy. Beside, I still have a question. How can we know this way is faster than that way? For example, is pop() faster or del() faster? I always think how can we know which way is the fastest way for programming. Lastly, I very enjoy the lecture and tutorial work, because they are interesting and fun.