Constants, Variables, and Arithmetic Operations

In this post, you will learn about Python variables, constants, and arithmetic operations. We'll also look at their use cases along with some examples that you can test on this page!

Variables

What is a variable?

A variable is a named location used to store data in the memory. Variables have a unique name know as an identifier. You might find it more useful to think of variables as a container that holds data which can be changed later throughout programming. Python has five standard data types:

• Numbers: a numeric value (int, long, float, or complex)
• String: a sequence of characters
• List: a changeable ordered sequence of elements; each element in a list is called an item
• All the items of a list can be of different data type
• Tuple: just like a list, except the elements or length of a tuple can't be changed
• All the items of a tuple can be of different data type
• Dictionary: an unordered collection of data values, used to store data values like a map

Creating a variable

Unlike other programming languages, Python has no command for declaring a variable. It automatically assigns a memory location as we assign the variable with a value. In other words, a variable is created the moment you first assign a value to it. Variables do not need to be declared with any particular type and can even change type after they have been set. 

You can use the assignment operator “=” to assign the value to a variable. Let's look at an example:

Assign Value to Multiple Variables

Python allows you to assign values to multiple variables in one line. You can also assign the same value to multiple variables in one line. Here's an example of both:

Naming Conventions for Variables

1. A variable name must start with a letter or the underscore character
2. A variable name cannot start with a number
3. A variable name can only contain alpha-numeric characters and underscores (A-z, 0-9, and _ )
4. Variable names are case-sensitive (age, Age and AGE are three different variables)

Constants

What is a constant?

A constant is a type of variable that holds values, which cannot be changed. In reality, we rarely use constants in Python. Constants are usually declared and assigned on a different module/file. Then, they are imported to the main file.

Assigning value to a constant

In Python, constants are usually declared and assigned on a module. Here, the module means a new file containing variables, functions etc which is imported to main file. To do so, in a file constant.py, define your constants. Then in another file main.py, import the constant and use. For example:

Naming Conventions for Constants

The naming conventions for constants are the same as for variables, with a few additional rules:

1. Use capital letters where possible to declare a constant. For example PI, GRAVITY etc.
2. Constants are put into Python modules and meant not be changed.

Arithmetic Operations

Arithmetic operators are used to perform mathematical operations like addition, subtraction, multiplication and division. They include the following:

• Addition: Adds values on either side of the operator
• Subtraction: Subtracts right hand operand from left hand operand
• Multiplication: Multiplies values on either side of the operator
• Division: Divides left hand operand by right hand operand
• Modulus: Divides left hand operand by right hand operand and returns remainder
• Exponent: Performs exponential (power) calculation on operators
• Floor Division - Division that results in a whole number adjusted to the left in the number line

Your turn!

If you want to try any of the code for yourself, all you have to do is copy it and paste it into the compiler below, and then hit run! Remember, if you declare a variable, you should add a print statement for the console to display it.

Sources:

https://www.programiz.com/python-programming/variables-constants-literals

https://www.w3schools.com/python/python_variables.asp

https://www.programiz.com/python-programming/operators