Python Basics

Python is an unambiguous, easy-to-read, general-purpose, high-level programming language that considers structured, procedural, and object-oriented programming paradigms.

Install Python

It’s easy to install Python. You need to follow a few steps.

First, you need to download Python from the official website. Just go to https://www.python.org/ and choose the latest version of Python (currently 3.7).

Once you have downloaded the installer, just run it and follow the instructions on the screen. It’s really straightforward, click “Next” a bunch of times and you should be done in less than 5 minutes.

Once Python is installed, you should be able to run it from the command prompt (on Windows) or from the terminal (on macOS and Linux). Just type “python” and hit Enter, and you should see something like this:

Python 3.7.0 (v3.7.0:1bf9cc5093, Jun 27 2018, 04:58:27) [MSC v.1914 32 bit (Intel)] on win32
Type “help”, “copyright”, “credits” or “license” for more information.

That’s it! You have now successfully installed Python on your computer

Set up a Python development environment

Installing Python is generally easy, and nowadays many Linux and UNIX distributions include a recent Python. Even some Windows computers (notably those from HP) now come with Python already installed.

If you do need to install Python and aren’t confident about the task you can find a few notes on the BeginnersGuide/Download page, but installing Anaconda or ActiveState Python is usually much easier.

Once you have installed Python you need to choose an editor.

Write your first Python program

In order to write your first Python program, you will need a text editor. A text editor is a program that allows you to create and edit text files. Some examples of popular text editors include Microsoft Word, Notepad++, and gedit.

Once you have chosen and installed a text editor, you are ready to write your first Python program. Python programs are typically written in a text file and saved with a “.py” extension. For example, you may save your program as “hello_world.py”.

To write your first Python program, open the chosen text editor and type the following:

print("Hello, world!")

This is a simple Python program that prints “Hello, world!” to the screen. To run this program,save it to a file with a “.py” extension and run it with the Python interpreter.

Python Syntax

In Python, syntax refers to the rules that determine how a program will be written and structured. Python is a very strict language, which means that even a small mistake can cause a program to fail.

Learn Python syntax basics

Python is a widely used high-level interpreted language that has efficient high-level data structures and a simple but effective object-oriented programming model. Although its syntax is somewhat different from other programming languages, Python’s indentation rules for blocks of code make it very easy to read.

Use the Python interpreter

To use the Python interpreter:

-Open a command prompt (on Windows) or a Terminal (on macOS and Linux). In the resulting command prompt or Terminal, type “python” and press Enter.
-The Python interpreter will appear. You can now type in Python code and press Enter to have it executed immediately.
-To exit the Python interpreter, type “exit()” and press Enter.

Write Python scripts

One of the most important aspects of programming is writing code that is easy for others to read. This is especially true for Python. Not only is Python syntax easy to read, but it is also easy to write. Python’s clean syntax rules make for a much smoother writing experience.

When you’re just starting out, it’s best to stick to writing simple scripts. You can always add more complexity later. For now, focus on getting the basic structure of your script down.

Here are a few tips to help you write Python scripts:

-Use a text editor like Sublime Text or Atom to write your code. These editors will highlight your code so that it’s easier to read.
-Save your scripts with a .py extension. This will let your computer know that these are Python files and they should be run with the Python interpreter.
-Make sure your scripts are encoded in UTF-8. This encoding will prevent errors when you try to run your code.
-Use comments in your code to explain what you’re doing. Comments start with a # sign and they can be placed anywhere in your script.
-Give your variables meaningful names so that you can easily remember what they represent. For example, use names like “first_name” or “current_year” instead of “x” or “y” .
-When you’re ready to run your script, open up a terminal window and type “python filename . py” . Make sure you include the extension!

Python Objects and Data Structures

Python is an object-oriented language, meaning that it views everything as an object. This can be contrasted with languages like C, which view data as more of a collection of individual elements. An object in Python is a collection of data and code that together perform a task.

Understand Python objects and data structures

Python is an object-oriented language, which means that it uses objects and data structures to store information. In Python, an object is a collection of data (variables) and functions (called methods) that work together to perform a task. Objects can be anything from a single value (like a number) to a complex data structure (like a database).

Data structures are the foundation of objects. They are the way that we store and organize information in Python. The most common data structures in Python are lists, tuples, and dictionaries.

Lists are ordered collections of data. Tuples are similar to lists, but they are immutable (meaning they cannot be changed). Dictionaries are unordered collections of data that are accessed by key, instead of by index.

In order to understand how objects work in Python, it is important to understand how data structures work. Data structures are the foundation of objects, and they define the way that information is stored and organized in Python.

Work with numbers, strings, lists, and dictionaries

Python is a versatile language that you can use on the backend, frontend, or full stack of a web application. In addition to its usefulness for web development, Python is also a great language for data science and scientific computing. Because Python is easy to read and has a concise syntax, it’s often the first language that new programmers learn.

In this course, you’ll learn the basics of working with numbers, strings, lists, and dictionaries in Python 3. You’ll also learn how to control the flow of your programs with conditionals and loops. By the end of this course, you’ll be able to confidently write basic Python code to solve problems.

Use Python modules and libraries

Python modules are code libraries that you can use in your own programs. Modules are usually stored in separate files and they have names that end with .py.

You can use any Python module by importing it using the import statement:

import module_name
Once a module is imported, you can use all the functions and classes defined in that module. For example, the math module defines a number of mathematical functions and constants:

import math
print(math.sqrt(4)) # prints 2.0
print(math.pi) # prints 3.141592653589793
You can also import only selected functions or classes from a module:

from math import sqrt, pi # imports only the sqrt() and pi functions from the math module
Or you can import all names from a module:

from math import * # this imports all names from the math module

Python Errors and Debugging

One of the most frustrating things when learning to code is dealing with errors. You can spend hours trying to figure out what went wrong, and sometimes it can be hard to find resources that explain the error in a way that you can understand. In this section, we’ll cover some of the most common Python errors and how to debug them.

Find and fix Python syntax errors

Python is a flexible language that can be used for much more than writing traditional programs. However, when you first start learning Python, you’ll likely encounter some errors and exceptions. This guide will help you find and fix some of the most common errors and exception types in Python.

Syntax errors
Syntax errors occur when your code is not valid Python. These are usually easy to fix because Python will tell you where the syntax error is and what kind of syntax error it is. For example:

>>> print('Hello world')
  File "<stdin>", line 1
    print('Hello world')
             ^
SyntaxError: invalid syntax

Debug Python programs

When you are writing a Python program, you may come across an error. There are different types of errors that can occur in a Python program. The most common type of error is a syntax error. Syntax errors occur when the structure of your code is incorrect. Another type of error is a runtime error. Runtime errors occur when your code is syntactically correct, but there is something wrong with the code itself.

In order to debug your Python programs, it is important to understand what type of error you are dealing with. Syntax errors are usually easy to fix, because you can see where the problem is in your code. Runtime errors are more difficult to debug, because you cannot always see where the problem is.

If you are having trouble debugging your Python programs, there are some tools that can help. The Python debugger, pdb, is a great tool for debugging Python programs. Pdb allows you to step through your code one line at a time. You can also set breakpoints in your code, so that pdb will stop execution at that point. This can be very helpful if you think you know where the problem is, but you want to make sure.

Another helpful tool for debugging Python programs is the trace module. The trace module allows you to trace the execution of your program. This can be very helpful if you cannot find the problem in your code. The trace module will print out each line of your code as it executes, so you can see where the problem is happening.

If you are still having trouble debugging your Python programs, there are many resources available online. The Python website has a section on debuggingPython programs (https://www.python.org/dev/peps/pep-0008/#debugging-python-programs). The Python mailing list (https://mailinglistsumpythepythonprojectcom/)is also a good place to ask for help with debugging Python programs

Handle Python exceptions

Exceptions are raised when a program encounters an error. Exceptions are handled using the try-except statement. The code that is executed when an exception occurs is placed in the except block.

When an exception occurs, the Python interpreter prints the traceback. The traceback includes the line number where the error occurred and the lines of code that were executed before the error occurred.

The try-except statement can be used to handle exceptions in Python. The try block contains code that may cause an exception to occur. If an exception occurs, the code in the except block will be executed. If no exception occurs, the code in the except block will not be executed.

Executing a Python program with anHandling Exceptions example
When you run a Python program, it may encounter an error and print a traceback. The traceback includes the line number where the error occurred and the lines of code that were executed before the error occurred. You can use this information to identify and fix errors in your Python programs.

Python Files and Databases

Python is a high-level, interpreted, general-purpose programming language, created on December 3, 1989, by Guido van Rossum, with a design philosophy entitled, “There’s only one way to do it, and that’s why it works.”

Read and write files in Python

Python has functions for reading and writing files. To read or write a file, you need to open it in Python using the open() function. The first parameter of the open() function is the path to the file, and the second parameter is the mode which defines how the file should be opened – ‘r’ for read-only, ‘w’ for write-only (overwriting any existing content), ‘a’ for append mode, ‘r+’ for reading and writing. You can also specify if the file should be handled as binary or text mode – ‘t’ for text mode (the default) and ‘b’ for binary mode.

Here’s an example of reading from a file:

f = open('filename.txt', 'r')
data = f.read()
f.close()

Access databases in Python

To access databases in Python, you need to use a database driver. A database driver is a set of programming instructions that enable Python to communicate with a specific type of database. Most Python database interfaces are written as modules in the Python Standard Library.

The most commonly used database driver for SQLite is the sqlite3 module. The sqlite3 module is already installed on your system. To use the sqlite3 module, you must first create a Connection object that represents the database. The Connection object is used to execute SQL commands and queries against the database.

SQLite is often used as an embedded database because it does not require a separate server process and can be easily integrated into applications using languages such as C and PHP. SQLite databases are also very portable because they are stored as regular files on the filesystem.

After you have created a Connection object, you can then create a Cursor object. The Cursor object is used to execute SQL commands and queries against the database. The Cursor object also allows you to iterate through the results of a query and fetch each row separately.

In addition to being able to execute SQL commands, the Cursor object also provides several methods for fetching data from the database:

cursor.fetchone() fetches the next row from the result set
cursor.fetchmany(size) fetches the next size rows from the result set
cursor.fetchall() fetches all remaining rows from the result set

Process CSV and JSON data in Python

CSV (comma separated values) and JSON (JavaScript Object Notation) are two popular types of data formats that are used for storing and transmitting data. Both CSV and JSON files are text-based, lightweight, and easy to transmit over the internet.

Though both CSV and JSON files can be opened and edited in a text editor, they have different uses. CSV files are best used for storing tabular data, such as a database or spreadsheet, whereas JSON files are better suited for transmitting data between different applications.

To process CSV and JSON data in Python, you need the following:

-A text editor (e.g., Sublime Text)
-The Python interpreter
-The csv module (for CSV files)
-The json module (for JSON files)

Once you have the above prerequisites installed, you can proceed with the following steps:

1)Open your text editor and create a new Python file.

2)Import the csv module by typing the following into your Python file: import csv.
3)Import the json module by typing the following into your Python file: import json.