Operators and Expressions in Python

In Python, operators are special symbols, combinations of symbols, or keywords that designate some type of computation. You can combine objects and operators to build expressions that perform the actual computation. So, operators are the building blocks of expressions, which you can use to manipulate your data. Therefore, understanding how operators work in Python is essential for you as a programmer.

In this tutorial, you’ll learn about the operators that Python currently supports. You’ll also learn the basics of how to use these operators to build expressions.

In this tutorial, you’ll:

• Get to know Python’s arithmetic operators and use them to build arithmetic expressions
• Explore Python’s comparison, Boolean, identity, and membership operators
• Build expressions with comparison, Boolean, identity, and membership operators
• Learn about Python’s bitwise operators and how to use them
• Combine and repeat sequences using the concatenation and repetition operators
• Understand the augmented assignment operators and how they work

To get the most out of this tutorial, you should have a basic understanding of Python programming concepts, such as variables, assignments, and built-in data types.

Getting Started With Operators and Expressions

In programming, an operator is usually a symbol or combination of symbols that allows you to perform a specific operation. This operation can act on one or more operands. If the operation involves a single operand, then the operator is unary. If the operator involves two operands, then the operator is binary.

For example, in Python, you can use the minus sign (-) as a unary operator to declare a negative number. You can also use it to subtract two numbers:

>>> -273.15
-273.15

>>> 5 - 2
3

In this code snippet, the minus sign (-) in the first example is a unary operator, and the number 273.15 is the operand. In the second example, the same symbol is a binary operator, and the numbers 5 and 2 are its left and right operands.

Programming languages typically have operators built in as part of their syntax. In many languages, including Python, you can also create your own operator or modify the behavior of existing ones, which is a powerful and advanced feature to have.

In practice, operators provide a quick shortcut for you to manipulate data, perform mathematical calculations, compare values, run Boolean tests, assign values to variables, and more. In Python, an operator may be a symbol, a combination of symbols, or a keyword, depending on the type of operator that you’re dealing with.

For example, you’ve already seen the subtraction operator, which is represented with a single minus sign (-). The equality operator is a double equal sign (==). So, it’s a combination of symbols:

>>> 42 == 42
True

In this example, you use the Python equality operator (==) to compare two numbers. As a result, you get True, which is one of Python’s Boolean values.

Speaking of Boolean values, the Boolean or logical operators in Python are keywords rather than signs, as you’ll learn in the section about Boolean operators and expressions. So, instead of the odd signs like ||, &&, and ! that many other programming languages use, Python uses or, and, and not.

Using keywords instead of odd signs is a really cool design decision that’s consistent with the fact that Python loves and encourages code’s readability.

You’ll find several categories or groups of operators in Python. Here’s a quick list of those categories:

• Assignment operators
• Arithmetic operators
• Comparison operators
• Boolean or logical operators
• Identity operators
• Membership operators
• Concatenation and repetition operators
• Bitwise operators

All these types of operators take care of specific types of computations and data-processing tasks. You’ll learn more about these categories throughout this tutorial. However, before jumping into more practical discussions, you need to know that the most elementary goal of an operator is to be part of an expression. Operators by themselves don’t do much:

>>> -
  File "<input>", line 1
    -
    ^
SyntaxError: incomplete input

>>> ==
  File "<input>", line 1
    ==
    ^^
SyntaxError: incomplete input

>>> or
  File "<input>", line 1
    or
    ^^
SyntaxError: incomplete input

As you can see in this code snippet, if you use an operator without the required operands, then you’ll get a syntax error. So, operators must be part of expressions, which you can build using Python objects as operands.

So, what is an expression anyway? Python has simple and compound statements. A simple statement is a construct that occupies a single logical line, like an assignment statement. A compound statement is a construct that occupies multiple logical lines, such as a for loop or a conditional statement. An expression is a simple statement that produces and returns a value.