Created by - Robert Kotaki
VARIABLES
Answer:The rules for naming and using variables in Python are:To avoid name errors when using variables in Python, one should ensure that the variable name is spelled correctly and that it has been defined before it is used. A name error occurs when a variable is used before it is defined, or when the variable name is misspelled. The Python interpreter provides a traceback that helps locate the source of the error. It is also helpful to use descriptive variable names that are easy to remember and to avoid using the same name for different variables in the same program.Code Examples:Let's start by creating a variable named x and assigning it the value of 5.makefileCopy codex = 5 We can print the value of the variable x using the print() function.scssCopy codeprint(x) Output:Copy code5 We can also perform operations on variables. For example, we can add two variables together and assign the result to a new variable.makefileCopy codex = 5 y = 10 z = x + y print(z) Output:Copy code15 Now, let's create a variable with an invalid name and see what happens.goCopy code4invalid_var = 2 Output:arduinoCopy code File "<ipython-input-1-93f1053b7d0c>", line 1 4invalid_var = 2 ^ SyntaxError: invalid syntax As we can see, an error occurred because the variable name starts with a number.Here's another example of a name error that can occur when a variable is used before it is defined.bashCopy codeprint(my_variable) my_variable = "Hello, World!" Output:csharpCopy codeNameError: name 'my_variable' is not defined As we can see, a name error occurred because we tried to print the value of my_variable before it was defined.To avoid name errors, we can define the variable before using it, as shown below.bashCopy codemy_variable = "Hello, World!" print(my_variable) Output:Copy codeHello, World! In summary, variables are used to store data in Python, and they are named according to certain rules. By following these rules and defining variables before using them, we can avoid name errors and make our code more readable and maintainable.
More detailsPublished - Tue, 11 Apr 2023
Created by - Robert Kotaki
Introduction to Lists in Python
Introduction to Lists in PythonIn this chapter and the next, we will learn about lists in Python. Lists are a powerful feature in Python that allow you to store and manipulate sets of information in one place. They are especially useful when dealing with large amounts of data.What is a List?A list is a collection of items in a specific order. You can put anything you want in a list, and the items in a list do not have to be related in any way. In Python, you can create a list using square brackets ([]) and separating the individual items with commas. It's a good idea to use a plural name for the list, such as "bicycles" or "names".Example:scssCopy codebicycles = ['trek', 'cannondale', 'redline', 'specialized'] print(bicycles) Output:cssCopy code['trek', 'cannondale', 'redline', 'specialized'] Accessing Elements in a ListLists are ordered collections, which means you can access any element in a list by telling Python the position or index of the item you want. In Python, index positions start at 0, not 1.To access an element in a list, write the name of the list followed by the index of the item enclosed in square brackets.Example:scssCopy codebicycles = ['trek', 'cannondale', 'redline', 'specialized'] print(bicycles[0]) Output:Copy codetrek You can also use string methods, such as title(), on individual items in the list.Example:scssCopy codebicycles = ['trek', 'cannondale', 'redline', 'specialized'] print(bicycles[0].title()) Output:Copy codeTrek Negative index values can also be used to access elements in a list, with -1 representing the last element in the list, -2 representing the second-to-last element, and so on.Example:scssCopy codebicycles = ['trek', 'cannondale', 'redline', 'specialized'] print(bicycles[-1]) Output:Copy codespecialized Using Individual Values from a ListYou can use individual values from a list just like any other variable. For example, you can use f-strings to create a message based on a value from a list.Example:scssCopy codebicycles = ['trek', 'cannondale', 'redline', 'specialized'] message = f"My first bicycle was a {bicycles[0].title()}." print(message) Output:cssCopy codeMy first bicycle was a Trek. Summary:A list is a collection of items in a specific order.Lists are created using square brackets ([]) and separating individual items with commas.Individual items in a list can be accessed using their index position.Index positions start at 0, not 1.Negative index values can be used to access elements from the end of the list.Individual values from a list can be used just like any other variable.
More detailsPublished - Tue, 11 Apr 2023
Created by - Robert Kotaki
STRINGS
IntroductionChanging Case in a String with MethodsUsing Variables in StringsAdding Whitespace to Strings with Tabs or NewlinesHere are some code examples to illustrate the concepts:bashCopy codename = "ada lovelace" print(name.title()) # Output: Ada Lovelace makefileCopy codefirst_name = "ada" last_name = "lovelace" full_name = f"{first_name} {last_name}" print(full_name) # Output: ada lovelace pythonCopy codefirst_name = "ada" last_name = "lovelace" full_name = f"{first_name} {last_name}" print(f"Hello, {full_name.title()}!") # Output: Hello, Ada Lovelace! swiftCopy codeprint("Languages:\n\tPython\n\tC\n\tJavaScript") makefileCopy codeLanguages:Python C JavaScript
More detailsPublished - Tue, 11 Apr 2023
Created by - Robert Kotaki
NUMBERS IN PYTHON
IntroductionIntegersExample:FloatsExample:Underscores in NumbersExample:Multiple AssignmentExample:ConstantsExample:
More detailsPublished - Tue, 11 Apr 2023
Created by - Robert Kotaki
Comments in Python
Introduction:Syntax:Example:bashCopy code# Say hello to everyone. print("Hello Python people!") What Kinds of Comments Should You Write?Tips for Writing Comments:Conclusion:
More detailsPublished - Tue, 11 Apr 2023
Created by - Robert Kotaki
MODIFYING, ADDING AND REMOVING ELEMENTS IN LISTS
Lists are dynamic, meaning that you can add, remove or modify elements as needed during the program’s execution. In Python, modifying a list element is done by assigning a new value to an element using the index operator [].This code will output ['ducati', 'yamaha', 'suzuki']. We've changed the first item of the list motorcycles from 'honda' to 'ducati'.To add an element to a list, Python provides several ways to add new data to existing lists.The simplest way to add a new element to a list is to append the item to the list. When you append an item to a list, the new element is added to the end of the list. The append() method is used for this operation.This code will output ['honda', 'yamaha', 'suzuki', 'ducati']. We've added the new element 'ducati' to the end of the list.You can add a new element at any position in your list by using the insert() method. You do this by specifying the index of the new element and the value of the new item.This code will output ['ducati', 'honda', 'yamaha', 'suzuki']. We've inserted the value 'ducati' at the beginning of the list.To remove an item from a list, you can use the del statement or the remove() method.If you know the position of the item you want to remove from a list, you can use the del statement.This code will output ['yamaha', 'suzuki']. We've removed the first item, 'honda', from the list motorcycles.If you know the value of the item you want to remove from a list, you can use the remove() method.This code will output ['honda', 'suzuki']. We've removed the item 'yamaha' from the list motorcycles.
More detailsPublished - Tue, 11 Apr 2023
Created by - Robert Kotaki
ORGANIZING A LIST
Introduction to ListsSorting a List Permanently with the sort() MethodpythonCopy codecars = ['bmw', 'audi', 'toyota', 'subaru'] cars.sort() print(cars) cars.sort(reverse=True) print(cars) sorted() function lets you display your list in a particular order without affecting the actual order of the list.We can display a list of cars in alphabetical or reverse-alphabetical order temporarily.Example code:Printing a List in Reverse Order with the reverse() MethodpythonCopy codecars = ['bmw', 'audi', 'toyota', 'subaru'] print(cars) cars.reverse() print(cars) len() function returns the length of a list.We can use len() to identify the number of items in a list.Example code:
More detailsPublished - Tue, 11 Apr 2023
Created by - Robert Kotaki
Avoiding Index Errors When Working with Lists
Avoiding Index Errors When Working with ListsWhen working with lists in Python, it's important to understand how indexing works to avoid index errors. This lecture will cover the basics of indexing in lists and provide some tips to avoid common errors.Indexing in ListsLists are indexed starting at 0, not 1.To access an item in a list, you use square brackets [] and provide the index of the item you want to access.If you provide an index that is out of range for the list, you will get an index error.To access the last item in a list, you can use the index -1.ExamplesLet's create a list of motorcycles and try to access the fourth item:scssCopy codemotorcycles = ['honda', 'yamaha', 'suzuki'] print(motorcycles[3]) This will result in an index error because there is no item at index 3. To fix this error, we need to remember that indexing starts at 0, so the third item in the list is at index 2. We can correct the code by changing the index to 2:scssCopy codemotorcycles = ['honda', 'yamaha', 'suzuki'] print(motorcycles[2]) This will correctly print the third item in the list, 'suzuki'.Let's try to access the last item in the list using the index -1:scssCopy codemotorcycles = ['honda', 'yamaha', 'suzuki'] print(motorcycles[-1]) This will correctly print the last item in the list, 'suzuki'.Finally, let's try to access the last item in an empty list:scssCopy codemotorcycles = [] print(motorcycles[-1]) This will result in an index error because there are no items in the list.Tips to Avoid Index ErrorsRemember that indexing starts at 0, not 1.Use the index -1 to access the last item in a list.If you get an index error, try printing your list or the length of your list to see if it is different than you expected.
More detailsPublished - Tue, 11 Apr 2023
Created by - Robert Kotaki
Working with Lists: Looping Through an Entire List
Working with ListsIntroductionIn this lesson, we will learn how to loop through an entire list using Python's for loop. Looping through a list enables us to perform the same action on each item in the list, making it efficient to work with lists of any length.Looping Through an Entire ListTo illustrate how to loop through a list, let's use an example of a list of magicians' names and print each name in the list using a for loop.pythonCopy codemagicians = ['alice', 'david', 'carolina'] for magician in magicians: print(magician) In the above code, we define a list of magicians' names and then loop through the list using a for loop. The for loop retrieves each name from the list, associates it with the variable magician, and then prints it to the console. This process is repeated for each name in the list.A Closer Look at LoopingWhen using a for loop, the set of steps is repeated once for each item in the list, no matter how many items are in the list. In the example above, the loop is repeated three times, once for each magician's name in the list.When writing a for loop, we can choose any name we want for the temporary variable that will be associated with each value in the list. However, it's helpful to choose a meaningful name that represents a single item from the list.Doing More Work Within a for LoopWe can perform any action on each item in the list using a for loop. For example, we can print a message to each magician in the list.pythonCopy codemagicians = ['alice', 'david', 'carolina'] for magician in magicians: print(f"{magician.title()}, that was a great trick!") In the above code, we add a personalized message to each magician in the list. The for loop retrieves each name from the list, associates it with the variable magician, and then prints a message to the console with the magician's name. This process is repeated for each name in the list.ConclusionIn this lesson, we learned how to loop through an entire list using Python's for loop. Looping through a list allows us to perform the same action on each item in the list, making it efficient to work with lists of any length. We also learned that we can perform any action on each item in the list using a for loop.
More detailsPublished - Tue, 11 Apr 2023
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