Hi in this video clip. Let me introduce "If clause". This is a case of an example of control statement. "If" clause is very important. And in this video clip, I briefly introduce the basic concept and basic use of "if" clause. In next module, I will explain in detail, the complex use of "if" clause. In this video clip, I show you a very simple example of "if" clause. And "if" clause always come with comparation operators. So first, let me introduce what are comparison operators. A few of them already introduced in previous videos clips. "x is great than y". The left side is how to write comparison operator and on the right side is the meaning. So "x" is greater than "y", "x" is less than "y", "x" is greater than or equal to "y". So greater than should come first than an equal sign. The location cannot be changed. "x" less than or equal to "y", again the symbols location, the two symbol locations cannot be changed. Two equal signs. This is "x" is equal to "y". The meaning is that "x" is the same as "y". But it means that you are comparing two values, whether they are the same or not. You are not assigning, if you use a single equal sign, it means that you are assigning "y" value to "x" not comparing them. So, don't get confused between the equal comparison or equal sign. Acclamation with equal sign. Not equal to. Again, you are comparing whether "x" it's not the same as "y".In the last case, if "x" is not the same as "y". True is returned. If they are the same false is returned. In the right above case, "x", double equal sign "y" means that if it is true, true value is returned. If it is not true, then false is returned. So the returning value is completely opposite between the two. "If clause". If there's a if clause, a comparison operation is implemented. And a condition is satisfied, then true value is returned. If not satisfied, false value is return. If you use only "if clause", if the condition met, the following command line will be executed. If the condition is not met, the following command, the line is not executed. So if only when condition is met a certain outcome is returned. If condition is not met, there are nothing reactions. But what if instead of simply using "if", you use, "if else" command lines? So the outcome is the same as above, but even though a condition is not met, an action will be implemented on the else statement. So this is difference. If you use only if statement when condition is not satisfied, there is no action on the computer. But if you use if-else statement, in that case, if a condition is satisfied, then a command line under if clause will it be executed. If the condition is not met, a condition under the else statement will be executed. So there's always actions, outcomes of that control statement. So, let me give you an example. Here "x" variable take an integer. If here's a comparison operator and this is header line. The header line always end with colon. This is the syntax. So, if "x" is equal to one, print, "x" has a value of one. Else if not, the second line of this print function will be executed, and the sentence will be printed. So let me give you "1" first, [hit] control + enter. Then if I put "1", then "x" has a value of "1" will be printed right? Yeah! But what about execute again that cell? Then again, what about I type "2"? Then, the second line "x" does not have a value of "1". This string sentence is presented. Then, in this case, what about "variable1" also take a number, and then there's only if clause. Another variable, "variable2", takes another number and comparing, and here's comparison operator. Then if-else statement is used. But in this case, the print function is getting a little bit messier. Here's text area and "variable1" value is printed and another text sentence. So, it, it becomes a full sentence, but string and variable, they are separate by comma. So, multiple components are inserted in the print function, and we are using it again. So, implementing. "Enter the first integer". So what about, let me give negative number "-1". Then obviously, the first integer is negative one, and its value is negative. Right? And then second number is asked. The second number is again, negative "-1", what about? Then obviously, the condition is met. The second integer is negative. And its value is negative one. Right? But what about we execute another one? So, we are executing the cell again. Then first integer. At this time let me give a positive number like "1", then no reaction. As I said before, when condition is not met, there's no reaction because there is no else statement. Only the condition is met, the print function is executed. Now, at this time, let me give again "1". Then what happens? Because of else statement, this print function is printed. So, the second integer is positive, and its value is "1". So, somehow if you use wisely the print function, you can print the full sentence by inserting the variable or mathematical operation formula inside the print function. Finally, let me introduce multiple statements in a single line, for example, two print command lines are consecutively written. But they are separate by semicolon, a semicolon. So one way of writing multiple command lines is using a semicolon. Each command line is separated by a semicolon. Then executing. "Hello" first-line is printed. And then "This is KOOC content" and "\n" which is inserted here. It means that because of this "\n", a new line is inserted, and line break is inserted "for Python basics", it becomes the third line. What if we delete "\n"? Then two lines are printed. So somewhere if you want to insert another line. So, printing a string in two lines, in that case, "\n" and then you can add one more line. So, again, before closing this video clip. Let me give you a review question, True or False: in an if-else statement, else should be indented. It is True or false, in an if-else statement else should be indented. It looks like else should be indented, but it shouldn't be indented. As you can see here. If-else statement, they are in the same rank. In the same rank. So, if after if you want to add else statement, it should not be in indented. So the answer is False, and this is the end of basic coding introduction of Python. But if you are really beginner of Python coding, rather than moving forward. What I mean by moving forward is before taking the next video clips or before studying the next module, you need to repeat and master the concept of coding introduced in this third module. Better to repeat. So, one way of mastering the content provided in the third module is restoring these codes. I'm not providing coding file in my MOOC course. If you want, by looking carefully at the video clips and typing them, you can recover or restore the information that I provided in these video clips. So, I recommended you to recover or restore the whole content that I provided that I used in this video clip.
