Python is a powerful, general-purpose programming language that is widely used in the software industry.
It is a popular choice for beginners because it is easy to learn, has a large and active community, and has a wealth of libraries and frameworks that make it useful for a wide range of applications.
In this guide, we will go over the basics of Python and how to get started with writing Python code.
Before you can start writing Python code, you need to have a Python interpreter installed on your computer.
There are many ways to install Python, but the easiest is to download the Python installer from the official Python website (https://www.python.org/) and run it.
The Python installer will give you the option to add Python to your system path. This is recommended, as it will allow you to run Python from the command line by simply typing “python” rather than the full path to the interpreter.
After installation, you can verify that Python is installed and working by opening a command prompt and typing “python.” This should open the Python interpreter, which will look something like this:
Python 3.9.0 (default, Oct 28 2021, 16:14:01) [GCC 8.3.0] on linux Type "help", "copyright", "credits" or "license" for more information. >>>
The >>> is the Python prompt, where you can type Python commands and have them executed immediately. You can exit the Python interpreter by typing “exit()” or pressing Ctrl+D.
Using an Integrated Development Environment (IDE)
While you can write Python code using a simple text editor, it is often more convenient to use an Integrated Development Environment (IDE) to write and debug your code.
An IDE is a program that provides a more feature-rich environment for writing code, with features such as syntax highlighting, code completion, and debugging tools.
There are many different IDEs available for Python, but some popular ones include PyCharm, IDLE (which comes with the Python installer), and Visual Studio Code. You can choose the one that best fits your needs and preferences.
Writing Your First Python Program
Now that you have Python installed and an IDE set up, you are ready to start writing your first Python program. Open your IDE and create a new file called “hello.py.” Then, type the following code into the file:
This is a simple Python program that prints the string “Hello, World!” to the screen. To run the program, save the file and then run it from the command line by typing “python hello.py.” You should see the output “Hello, World!” printed to the screen.
Variables and Data Types
A variable is a named location in memory where you can store a value. In Python, you can create a variable by simply assigning a value to it. For example:
x = 5 y = "Hello"
This creates two variables, x and y, and assigns them the values 5 and “Hello”, respectively.
Python is a dynamically-typed language, which means that you don’t need to specify the type of a variable when you create it.
The interpreter will automatically determine the type based on the value you assign to the variable. In the example above, x is an integer and y is a string.
Here are some of the common data types in Python:
- int: An integer is a whole number. In Python, integers can be as large as the memory of your computer allows.
- float: A float is a decimal number. In Python, floats are represented using double-precision floating-point numbers, which means that they have a lot of precision (up to around 16 decimal places).
- str: A string is a sequence of characters. In Python, you can create a string by enclosing a series of characters in single or double quotes. For example:
name = 'John' message = "Hello, World!"
- bool: A boolean value is a value that is either True or False. In Python, you can create a boolean value using the True and False keywords.
Operators and Expressions
Operators are special symbols in Python that perform specific operations on values. Here are some of the common operators in Python:
- +: The addition operator adds two values together.
- –: The subtraction operator subtracts one value from another.
- *****: The multiplication operator multiplies two values.
- /: The division operator divides one value by another.
- %: The modulus operator returns the remainder of the division of one value by another.
- ==: The equality operator tests if two values are equal. It returns True if the values are equal, and False otherwise.
- !=: The inequality operator tests if two values are not equal. It returns True if the values are not equal, and False otherwise.
Expressions are combinations of values, variables, and operators that Python can evaluate to a single value. For example:
x = 5 y = 10 z = x + y
In this example, the expression “x + y” is evaluated to 15, and the result is assigned to the variable z.
Control structures are statements in Python that control the flow of execution in a program. They allow you to specify which statements should be executed under which conditions.
Here are some of the common control structures in Python:
- if: The if statement allows you to execute a block of code if a certain condition is True. For example:
x = 5 if x > 10: print("x is greater than 10")
- for: The for loop allows you to execute a block of code multiple times, with a different value each time. For example:
for i in range(5): print(i)
This code will print the numbers 0 through 4 to the screen.
- while: The while loop allows you to execute a block of code multiple times as long as a certain condition is True. For example:
x = 0 while x < 5: print(x) x += 1
This code will print the numbers 0 through 4 to the screen.
Functions are blocks of code that are defined and can be reused multiple times in a program. Functions are useful because they allow you to encapsulate a specific piece of functionality and use it multiple times without having to write the same code over and over again.
In Python, you can define a function using the def keyword, followed by the name of the function and a set of parentheses. For example:
def greet(name): print("Hello, " + name + "!")
To call a function, you simply need to type the name of the function followed by a set of parentheses and any necessary arguments. For example:
This will print “Hello, John!” to the screen.
Functions can also return a value using the return keyword. For example:
def add(x, y): return x + y result = add(5, 10) print(result)
This will print 15 to the screen.
Modules are files that contain Python code that can be imported into other Python programs. Modules are useful because they allow you to reuse code across multiple programs, and they make it easier to organize your code into logical units.
In Python, you can import a module using the import keyword, followed by the name of the module. For example:
import math x = math.pi print(x)
This will print the value of pi (3.14159…) to the screen.
You can also import specific functions or variables from a module using the from keyword. For example:
from math import pi print(pi)
This will also print the value of pi to the screen.
Object-Oriented Programming (OOP) is a programming paradigm that is based on the concept of “objects,” which are data structures that contain both data and functionality. OOP is useful because it allows you to organize your code in a way that is more intuitive and easier to maintain.
In Python, you can create a class using the class keyword, followed by the name of the class and a set of parentheses. For example:
class Dog: def __init__(self, name, age): self.name = name self.age = age def bark(self): print("Woof!") dog1 = Dog("Fido", 3) dog2 = Dog("Buddy", 5) print(dog1.name) print(dog2.age) dog1.bark()
This code creates a class called Dog with a constructor (init) method that is called when a new object is created. It also has a bark() method that prints “Woof!” to the screen.
The self parameter is a special parameter in Python that refers to the current object. It is used to access the attributes and methods of the object.
Inheritance is a way to create a new class that is a modified version of an existing class. The new class is called a subclass, and the existing class is the superclass.
The subclass inherits all of the attributes and methods of the superclass, and can also have additional attributes and methods of its own.
In Python, you can create a subclass using the class keyword, followed by the name of the subclass and the name of the superclass in parentheses. For example:
class Animal: def __init__(self, name, species): self.name = name self.species = species def make_sound(self): print("Some generic animal sound") class Dog(Animal): def __init__(self, name, breed): super().__init__(name, species="Dog") self.breed = breed def make_sound(self): print("Woof!") dog1 = Dog("Fido", "Labrador") print(dog1.name) print(dog1.species) print(dog1.breed) dog1.make_sound)
This code creates a subclass called Dog that inherits from the Animal superclass. The Dog class has its own init method and make_sound method, which override the ones in the superclass.
When the dog1 object is created and the make_sound method is called, it will print “Woof!” to the screen rather than the generic animal sound.
This guide provides an overview of the basics of Python and how to get started with writing Python code.
Of course, there is much more to learn about Python, but this should give you a good foundation to build upon. As you continue to learn and work with Python, you will find that it is a versatile and powerful language that is well-suited to a wide range of applications.