PYTHON CRASH COURSE: Beginner guide to Computer Programming, Web Coding and Data Mining. Learn Machine Learning, Artificial Intelligence, NumPy and Pandas packages with exercises for data analysis. by Test Jason

Author:Test, Jason [Test, Jason]
Language: eng
Format: azw3, epub
Published: 2020-07-27T16:00:00+00:00

yourself if you need to consider several solutions before you come up with a reasonable way to make it work; if so, write a comment on your answer.

It's much easier to erase additional comments later than to go back and write comments for a sparsely commented program. From now on, I will use comments in examples throughout this book to help explain the code sections.

What Is a List?

A list is a set of items in a given order. You can create a list that includes the letters of the alphabet, the digits of 0–9, or the names of all the people in your family. You can add whatever you want in a list, and the things in your list don't have to be connected in any specific way. Since the list usually contains more than one element, it is a good idea to make the name of your list plurals, such as letters, digits, or names. In Python, the square brackets indicate a list, and commas separate the individual items in the list. Here's a simple example of a list containing a few types of cars:

bicycles.py cars = ['trek', 'cannondale', 'redline', 'specialized'] print(cars)

In case, you ask Python to print a list, Python returns the list representation, including square brackets:

['trek', 'cannondale', 'redline', 'specialized']

Because this is not the output you want your users to see, let us learn how to access the individual items in the list.

Accessing Elements in a List

Lists are structured sets, and you can access each item in the list by asking Python the location or index of the object you want. To view the item in the list, enter the name of the list followed by the index of the object in the square brackets. Let us take the first bike out of the bicycle list, for example:

cars = ['trek', 'cannondale', 'redline', 'specialized'] u print(cars[0])

The syntax for this is shown in U. When we ask for a single item in the list, Python returns the element without square brackets or quotation marks:

trek

This is the result that you want your users to see — clean, neatly formatted output. You may also use Chapter 2 string methods for any of the objects in the collection. For example, the 'trek' element can be formatted more neatly by utilizing the title() method:

cars = ['trek', 'cannondale', 'redline', 'specialized'] print(carss[0].title())

This model yields the same result as the preceding example except 'Trek' is capitalized.

Index Positions Start at 0, Not 1

Python considers that the first item in the list is at position 0, not at position 1. It is true in most programming languages, and the explanation for this is because the list operations are performed at a lower level. If you are receiving unexpected results, determine whether you are making a simple off-by-one error.

The second item on the list has an index of 1. Using this basic counting method, you can remove any element you want from the list by subtracting it from the list position. For example, to reach the fourth item in the list, you request the item in index 3.

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