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As a programmer, you you'll spend 60% of your time coding and 40% of your time fixing bugs.

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So it's very important to understand what errors are and how to fix them.

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So let's revise.

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Errors.

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We have two types of errors, actually.

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We have syntax errors and we have exceptions.

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So syntax errors are errors which happen before the interpreter.

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Compiles the codes.

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So first the interpreter just checks the syntax, right?

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It looks if you have the brackets correctly, the commas, the dots.

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For example, this line here.

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This starts with a square bracket, but it ends with a parentheses.

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The correct code would be to have a closing parentheses here.

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But that is not the case.

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And that's why this code will return of this.

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The results.

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So this is a syntax error.

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An error which happens before the code is compiled and executed for the processor.

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So this year tells you with this arrow where the error is, so closing parentheses does not match.

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Opening parenthesis.

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Right.

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That's quite clear.

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But error messages are not always clear.

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Let's look at this one here.

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Right.

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So we have this opening bracket.

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We have this closing bracket.

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That's fine.

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But instead of the periods between the variable and the methods, we have a comma here.

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So this should be a period.

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In that case, we get a syntax error, of course, because the syntax is not correct, but the error

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is not so clear.

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The message it says that we forgot some parentheses around the comprehension target.

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So the interpreter looks at these two and it thinks that perhaps you meant to have them inside parentheses

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like that.

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So it's not so clear for the interpreter to understand what you're actually doing.

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So in that case, you should look carefully at the codes and try to use your experience to understand

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where the syntax error actually is.

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So in that case, this comma should be replaced with.

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A period.

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So these two were examples of syntax errors.

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Then we have exceptions.

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This code here is syntactically correct.

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So all the symbols and the rules of the language syntax are respected.

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But the problem here is that we have this variable which doesn't exist.

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So the variable name itself is fine.

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It's syntactically correct, but it has not been declared in the script.

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That's why we get this name error.

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So we have syntax errors and we have nightmares.

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And then we have attribute errors, which is produced by this code, for example.

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This is an attribute error because this method here has been mistyped.

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There is not such a method for strings.

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The correct method would be strip.

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So in that case you get this attribute error.

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So an attribute a method is actually an attribute.

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So.

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Here we are trying to access that strip attributes out of the string object.

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That's why we get this error.

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STR object has no attribute strip.

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So such errors are caught when the interpreter is trying to compile the codes to make sense of the codes.

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Here is another example.

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So we asked the user to enter a number such as the year of birth, and then we have this variable currency

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here.

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Then we want to calculate the age of the person using the current year minus the year of birth for that

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person.

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And we print out age, but the user didn't enter the actual year, but they entered something like this,

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right?

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In that case, this produces a value error.

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It says that this thing cannot be.

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Convert it into an integer.

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So the INT method expects something like a string which contains a number inside.

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For example this here, but this is not really a number.

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It contains some dots and things like that.

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And that brings us to the.

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Topic of handling exceptions.

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Okay, so these are exceptions, value error, attribute error.

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These are known as exceptions and try accepts helps us to predict an error.

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So we get that code and we transform it into this code.

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So we tried to get the input from the user.

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We tried to convert it into an INT, and then we tried to calculate the age and then we print out the

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age.

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So if the user will enter the ear correctly, for example, 3001.

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This code will be executed.

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So in other words, where there are no errors, this code will be executed.

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But if this code produces an error, then Python will execute this code.

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Now it's better that instead of doing except here you should mention the actual error that you accept.

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Which you expect.

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So in this case, we expect a value error when the user doesn't enter a correct format, Right.

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Like this one.

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So it's it's better to specify the error specifically in here.

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Now, this line here, it's better to keep it outside of this tri, except because.

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You don't really expect an error in this declaration.

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So mostly you want to put these dynamic codes inside the try block So whenever possible, try to put

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other codes outside of the tri block.

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If you can.

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Otherwise it's fine.

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If this was also inside this block.

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Somewhere in here.

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Right.

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That would also be fine.

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It's important to know that tri accepts does not catch syntax errors because try accepts only catches

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exceptions which are codes when the interpreter is trying to compile the code.

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So this code here, for example, has this age variable which is missing a parentheses.

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So in that case, if you run this code you'll get a syntax error.

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So the try block the try clause will not be able to catch that syntax error, which is a good thing.

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So first of all, you always want to have your code syntactically correct.

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Then you catch all the exceptions.

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And then you might have the question, oh, when to use, accept and when to use even live else.

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Well, here is an example of when you use a fails or if it fails.

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So the try accepts block always catches errors.

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It doesn't catch logical errors or logical cases.

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For example, if you you want to tell the user that, oh, you're the age we calculate it for you is

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too big, then you would want to find that out with an if condition here.

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Because the interpreter doesn't know what a normal age is.

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It doesn't know that humans cannot be 150.

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So you have to use if else blocks for that.

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Right.

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Next topic comments and doc strings.

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So this year is a docstring doc strings are used to document what a function does, so you place them

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inside the function definition and you use these triple quotes here and there.

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So this function is then called in here and then for commenting single lines of code or blocks of code

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which are not functions, then you use comments.

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So this comment here is telling something is trying to tell us something about the next line which is

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placed underneath.

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So this one.

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But try to not overuse comments, for example.

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I think this comment here would be unnecessary because it's clear to the programmer that you're actually

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calling the function here so you can omit this comment.

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So you only want to comment complex code which you think that it will be harder to understand if you

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come back two weeks after or something like that.

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Modules.

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Modules are Python files which can be imported into another Python file.

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So basically when you import my file, my file is a file named my file dot py.

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And so when you import that python file, you are making available all the functions and the variables

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that that script has inside.

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So in here, let's say this my file that SPI script had this area function defined.

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So let's suppose that this area function was defined in my file, that's P In that case, we can access

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that by referring to my file dot area and then we call that area function and get the output in a variable.

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Standard libraries are also.

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Python files.

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They can be one single dot P file or multiple files.

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For example, glop is a standard library request is a standard library.

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So these are libraries which you don't have to install.

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These are included with Python.

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So you just import them and then of course, you use them similarly as we did with this.

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So my file area.

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Glop that glop.

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So glop is a function in the glop library area is a function in the my file module.

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So this is a local module and this would be a standard library or a standard module.

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You can see depending of whether this is a single file or multiple files.

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So that particular function globe would return this list.

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Now, sometimes you don't really know if that is a method or a function.

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So if Globe is a library or a module, then this is probably a function.

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But if this was a class, then this would have to be called a method.

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Now it's really it doesn't matter much what you call this, a method or a function.

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But if you really want to find out in part charm, you can right click and then you can go to the go

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to menu and then go to implementations.

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And there you will see what this really is.

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If it's inside the glob that P file or if it's inside a class.

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Right.

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So here I've also tried to use the get function of the requests library so that it's used to get the

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contents of a website and then print it out.

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So the content is HTML, as you can see here.

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It also contains other information which is inside the HTML, for example, this text here.

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And so one third party libraries are libraries which have not been included with the Python interpreter.

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So you have to install them with PIP installed followed by the library name.

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Their behavior is, of course, the same as the standard library.

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So you use them using the same syntax, Of course.

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Web apps.

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Web apps needs a third party library, also known as a framework, a web framework such as Tremlett.

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So we did use Tremlett in the course, and we'll use it again to create more complex web apps.

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So I'm not going to go deeper into explaining Web apps because we're going to work over and over again

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with them throughout the course.

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We also covered p one simple Google a library to create desktop apps.

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We're going to have more Google apps in the course.

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So I'm not going to explain those here as well.

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So you have a chance to practice and practice these over and over again throughout the course, either

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by instructor led projects or by your own projects, which I'll give you.

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I'll hand you out the exercises, the requirements, and you'll be able to work on your own.

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So thanks for following this series of reviews.

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And let's move on to the real parts of the course building applications.

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So it's going to be fun, I promise.

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And I'll see you in the next video.