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Why Initializing Variables Matters

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Crash Course on Python

4.7（630 個評分） | 24K 名學生已註冊

課程 1（共 6 門，Google IT Automation with Python 專項課程）

This course is designed to teach you the foundations in order to write simple programs in Python using the most common structures. No previous exposure to programming is needed. By the end of this course, you'll understand the benefits of programming in IT roles; be able to write simple programs using Python; figure out how the building blocks of programming fit together; and combine all of this knowledge to solve a complex programming problem. We'll start off by diving into the basics of writing a computer program. Along the way, you’ll get hands-on experience with programming concepts through interactive exercises and real-world examples. You’ll quickly start to see how computers can perform a multitude of tasks — you just have to write code that tells them what to do.

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您將學習的技能

Basic Python Data Structures, Fundamental Programming Concepts, Basic Python Syntax, Python Programming, Object-Oriented Programming (OOP)

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4.7（630 個評分）

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DM

Jan 28, 2020

Very straight forward class. I like the structure of the videos and text to read-along with. The prompts within the video to make sure you're listening was a nice addition.

JM

Feb 07, 2020

Good course for the beginners. It is awesome for beginners. The exercises and the demo in the videos are cool. Balanced course with implementations as well as theory.

從本節課中

Loops

In this module you'll explore the intricacies of loops in Python! You'll learn how to use while loops to continuously execute code, as well as how to identify infinite loop errors and how to fix them. You'll also learn to use for loops to iterate over data, and how to use the range() function with for loops. You'll also explore common errors when using for loops and how to fix them.

Introduction to Loops1:58

What is a while loop?3:12

More while Loop Examples3:14

Why Initializing Variables Matters3:49

Infinite Loops and How to Break Them4:08

教學方

Google

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腳本

[MUSIC] As we've called out earlier writing loops allows us to get our computer to do repetitive work for us. So this is one of the main benefits of writing scripts in IT is to save time by automating repetitive tasks, loops are super useful. So let's make sure you avoid some of the most common mistakes people make when writing loops. One of the most common errors is forgetting to initialize variables with the right value. We've all made this mistake when starting to code. Remember how in the earlier examples we initialized our variable x to 0 in one case and to one in the other. When we forget to initialize the variable two different things can happen the first possible outcome and the easiest to catch is that Python might raise an error telling us that we're using a variable we haven't defined, which looks like this. As we've done with other errors we've come across, we can look at the last line to understand what's going on. This error type is a name error and the message that comes after it says we're using an undefined variable. It's straightforward to fix, we just need to initialize the variable before using it like this, Fixed. Now, there's a second issue we might face if we forget to initialize variables with the right value. We might have already used the variable in our program. In this case, if we reuse the variable without setting the correct value from the start, it will still have the value from before. This can lead to some pretty unexpected behavior. Check out the script, can you spot the problem? In the first block, we correctly initialize x to 1 and sum to 0 and then iterate until x equals 10 summing up all the values in between. So by the end of that block, sum equals the result of adding all the numbers from 1 to 10 and x is 10. In the second part of the code, the original intention was to get the product of all the numbers from 1 to 10, but if you look closely, you can see that we're initializing product but forgetting to initialize x. So x is still 10, this means that when the while condition gets checked, x is already 10 at the start of the iteration. The while condition is false before it even starts and the body never executes. Let's see how this problem would look. In this case, it might be harder to catch the problem because python doesn't raise an error. The problem here is that our product variable has the wrong value. If you have a loop that's gone rogue and not behaving as expected, it's a good idea to check if all the variables are correctly initialized. In this example, we need to set x back to 1 before starting the second loop. As always, the best way to learn is to practice it yourself. Makes sense? Remember, if you ever feel stuck or a little unsure about something you can always ask for help in the discussion forums. These forums are there to let you get the help you need when you need it, so don't forget to use them. So, to recap, whenever you're writing a loop check that you're initializing all the variables you want to use before you use them. And don't worry if you don't get it right the first time, we've all been there when learning how to code. As we've called out before, the way to master programming is to practice, practice, practice. Keep practicing until you're comfortable and even then it's still okay to make mistakes. So don't feel like you can't or loop back around to review and practice everything we've covered so far.

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