Hi everyone. What are we studying? So far we have studied many concepts and tools provided by Python, but the tools that we are studying right now all are coming from basic Python or standard library of Python. Let me introduce the standard library of Python. Standard library of Python includes the basic tools, all the basic tools of Python coding. Here's a document provided online, so let me click it then the web page pops up. This is a web page explaining or reviewing standard libraries. There are so many functions and instances or constant values. There are so many tools but I'm selecting some of them which is often used in AI coding, so this is especially focused on AI coding. I'm introducing the tools very often used in AI coding. I'm not going to introduce the details, but in this place you can learn about the specific functions; the concept and how the tools are working. Now, there are popular modules provided in standard library math. This is what I already introduced to you. Random, this module we are going to use. Csv is a tool for importing or saving CSV files. There are so many tools. Math module, for example, if you want to look into the details of math module. On the standard library, there is math module homepage here. If you go to mathematical functions included in math module, are explained here. There are many functions also you can use, so you refer to whenever you need a function. Then let me introduce how to use Tab key for completing object name or identifiers. For example, you don't remember fully the name of object, or name of function, or name of class. In that case, for example, you remember, a part of name which is ma. You want to know what are the functions or objects existing in standard library? Simply you place that cursor at the end of ma and press ''Tab" key. Here, many options you get: map, max. Those are the objects or commands you can use which is starting with ma words. Using Tab key, you can easily find out. In order to get out, press "Esc", Escape key. Now, if you want to know the functions belonging to math module as it is written here, math.?, then press "Tab" button. Then as you have seen above here, this kind of window will appear and you can browse the functions available in a math module. Now, let me introduce the Methods concept. Methods are functions you can call on your object. Methods are functions, but when functions are specifically used they are called methods. Actually, in previous video clip, once I used the terminology Method but here I am explaining its concept. In order to use function as a method, you use this syntax. A function is called on this object of data, that is the method. Sometimes you need to provide argument values. One example is here, you create Youngsun Kwon string object here and assign that string value to my_name. You want to turn all the string values into lowercases, in that case, you use lower function. If you turn all the values into capital letters, you use upper function. This print function applies methods lowercase and uppercase for the two object, my name. And then finally at the third, the original content, original string builder will be returned. Let me execute it. What happens? Youngsun Kwon, the name turned into all lowercase values, and then uppercase values, capital letters, and then that original my_name, string value. This is a way of using function as a method. I already have shown you how to import pi files. In the previous video clip, I imported just one pi file, but what about libraries? Like math library, I can code it as a module, but actually, it is part of a standard library, but it contains so many functions you can use, built-in functions, that's why a module can be also called a library. You can either use module or library. For example, if you want to use the functions included in math module, you need to import math. But at this time, math is just the four letters. Rather than assign nickname, or shorten the name and may, you simply use math. In order to use function or a constant value pi you need to use math.pi, it looks like method calling. You are calling pi on this object but math is a library name actually, it is also object so similarly, you can understand this is as a way of using a method concept. Sometimes, rather than inputting all the functions available in math manager, you want to specifically import a few functions. In that case, you use this syntax from math. You specify ceil and sum. In this case, what is the benefit of using importing specific functions from math module. In that case, you don't have to add, you shouldn't actually add the math. Like math.pi, you simply use ceil or sum. Importing a library whether abbreviated name, this is what I already explained. For example, statistics module you imports statistics module as a stat because it is shot. When you call specific function included in statistics module or library, instead of using statistics, you use a shorter name stat. This is a way of importing libraries for your coding. One example is provided here. First case is import math, but what about which one we use first? This one, we are specifically importing specific functions ceil, floor, pi. Ceil is, rounds a number up to or largest integer. Floor rounds numbers down to the nearest integer. Two functions actually return integer values. Ceil returns or rounds a number up to the nearest integer, up to, not done. In this case, print (pi, ceil (9.8), the answer will be 10, because rounding up; floor rounding down, so nine will be returned, and x list is created and calculating mean, Ricci belongs to a stat module. In this case, we imported statistics using stat shortened the name. We execute it then what happens? Pi value printed 10,9 is returned. But what about rather than importing this way, we import this one? Mass. We are importing all the functions without calling specific function. In their case, if we use this syntax, what happens at a message where stanza? Well, because we already imported the tools so we need to clear. Then what happens at a message? It comes out, right? Because our steadies not defined, but because two modules are imported. But I put hash sign in a wrong place, I put that here, I should have put hash sign here. Hash sign here, and a message disappears, but still in working space. All the tools are existing, clear again, then what happens? We run this one, at a message because at this time you need to put mass in front of pi. Because we imported all mass functions generally not specifying specific functions available in math module. In that case, we have to use this one. Now we'd run this cell then, no problem at all. Depending on how you import, your syntax should be changing. The questionnaires, true or false. The syntax from library name input tools allows you to use the tools without the library name, is it true or is it false? Yes, it is true. Right?