Hi everyone. We are now ready for coding. But before starting to code with Python, let me explain basic rules and concepts, very basic rules and concepts of Python. First, let me show you the big picture of this course. Through this course, we are learning the Standard Library of Python. And then we are also learning NumPy, Pandas, Matplotlib, and Seaborn. And finally, we are also learning OOP, Object-Oriented Programming. Basically, which is about making classes. So Python is composed of many libraries, but there are key libraries. Key libraries are standard library, which is basic Python, and then NumPy, which is focused on numerical analysis and built on the Standard library. We are learning array-type data handling. In pandas. Pandas is also built on NumPy, which is also built on the Standard library. Pandas is about panel data manipulation and operation. So, they are key data processing libraries, and finally, there are two more libraries, which are popular for visualiazation. One is Matplotlib and Seaborn. So, in this course, I will briefly explain how to use two tools for data visualization. Then we are starting classes, how to make classes. So, my course is all about those five components. After completing this course, you can start Machine learning coding and Deep learning coding with Scikit-learn and TensorFlow. Now let me introduce the basic blocks of Python one by one. The first concept you need to learn is identifier. So, an identifier is name of an object. So you create, you assign, identifiers for each object. In this case, class, function or variables are all objects you create, but you need to be able to recognize which one is which. So, an identifier is making names of the objects that you created. What information can you use for making identifiers? First, letters, all English letters, you can use for making names of objects that you are creating. But letters are case sensitive in Python. It means that capital 'L' is differently treated that lowercase 'l', so case sensitive. All letters can be used for making names. And also, any digits between 0 to 9 can be used for making name. Or sometimes, you can also use underscore. Underscore, sometimes named also under bar. For example, "_R" or "_d." This is different from "R," and this is different from "d. " So under bar can be used. Surely, the under bar can be used at the front, but sometimes it can be used at the end. Yeah. So and also in the next slide, I will introduce keywords. Those reserve words or reserved letters used by Python. So, you cannot use keywords as part of your identifiers. This is an agreed rule among Python creators. And also you can use numbers, an interger between zero to nine, but you cannot put the number first when you make a name of something. So "x9" is good, but "9x" cannot be used. So, it means that name of objects starts with letters. It can be either lowercase or capital letter, upper case. And also, you can use digits, but digits cannot be the first character of your object name. And also, for naming, you cannot use special symbols, like "%", "$", and/or "!" signs, those are the rules you need to keep that in mind when you are assign a name for any object that you create. Keywords, keywords are reserved words to define the syntax and structure of Python. So, keywords, all are in lowercases except for, "True, False and None," three cases. Only in three cases, the first letter is a capital letter. So, "True, False, None" for example "or”, “and”, “as”, “with”, “import”, “from”, “is." Those words are keywords. So, don't use those words as the name of your object. "if" this is actually lowercase "elif", "else", "not" this is also for lowercase "for", "for", "in", "while," those are all reserved keywords. So, don't use them as your name of objects. So those are all lowercases. Simply they automatically changed as capital letters because they comes first. Indentation rule. Python is you using indentation rule. It is a kind of a mandatory rule. So you need to follow this indentation rule. Each line of a code must be indented by the same amount for it to belong to the same block of code, which means that if the indentation is different, then the different code, it is not belonging to the same block of code. So indentation rule is forced by the developers of Python. So, you have to follow. I will show you how you can do it. But indentation increases the clarity of coding. So, it is good rule to follow. Another term that I need to introduce is the "Suite", the concept of a "Suite", but don't have to remember all those things. As you do code, you will get familiar with them. I'm just introducing key concepts, but you don't have to remember memorize. As you do coding, you will acquire them naturally without trying to memorize them. Suite,, suite are lines, of code starting with a header line in control statement. One good example is one. This is a kind of a creating a loop for loop. It starts with "for" and those are the syntax. It is the header line. The first line is the headline. And headline. And headline always end with this colon sign ":”. Yeah. And those following codes are indented by this amount. So, this is following indentation rule. So those commands are part of the whole block. Suite of code, and here's also another headline with a colon. Then another indentation is inserted. It means that this line of code only belongs to this one, but the whole belongs to this for loop. So, the header line begins with a keyword like "for" here, yeah as we said, there are so many keywords, but it ends with a colon. So this is a part of code block separated that is the "Suite". Especially it is used to in control statement. Block. Block is simply a chunk of codes, but it is often lines of codes in functions. Soon, we are going to learn what is functions, how we make functions in Python. So a function is composed of a few lines in some cases, many, lines in other cases. So that function code becomes a kind of block. Snippet. Snippet is simply a small portion of code. You can use a snippet or a line of code, or a block of code or a suite or code. Basically, they are a group of coded lines. A review question, which identifier is wrong? So you can use letters, right and also numbers. This one is no problem. Right? And under bar or underscore is used between text letters, and "k9k" is okay because the number is in between two characters, "5dog!" "k20", which one is wrong? Actually, obviously this is wrong. Why? Because number cannot come first. So that is the case of wrong naming of the object.
