Expression in Python

Last Updated on March 2, 2023 by Prepbytes

This article will provide an in-depth look at the expression in Python. It will cover the types of expressions, the use of multiple operators, and the difference between statements and expression in Python.

What is Expression in Python?

Expression is a fundamental concept in the Python programming language. They are a combination of values, variables, and operators that the interpreter can evaluate to a single value. The expression in Python can be used in various forms, including as part of a larger statement or standalone.

Expression in Python is a sequence of characters that represent a value or a computation. They are used to perform operations on data, such as mathematical calculations, logical evaluations, and string manipulations. Expression in python is a fundamental aspect of programming and are used to create variables, control flow, and define functions.

In Python, an expression is a combination of values, variables, and operators that evaluates to a single value. Expression in python can be used in a variety of ways, such as in assignment statements, function arguments, and conditional statements.

Evaluation of Expression in Python:

When an expression is encountered in Python, the interpreter evaluates it to a single value. This evaluation process is known as "expression evaluation." The evaluation process begins with the innermost set of parentheses and works outward. The interpreter evaluates each operator and operand in the expression based on its precedence and associativity. For example, in the expression 2 + 3 4, the multiplication operator () has higher precedence than the addition operator (+), so the interpreter will first evaluate the multiplication of 3 and 4, resulting in 12, and then add 2 to that result. This results in the final value of 14.

Types of Expression in Python with Examples:

There are several types of expression in Python, but in this article, we will majorly focus on arithmetic, comparison, and logical expressions.

Arithmetic Expression in Python:

In Python expression, arithmetic expressions are used to perform mathematical operations such as addition, subtraction, multiplication, and division. These expressions can be used in a variety of ways, such as in assignment statements, function arguments, and conditional statements. Understanding the basics of arithmetic expressions is essential for writing efficient and effective code.

Types of Operators:

Python expression provides a variety of operators that can be used in arithmetic expressions. These operators include:

• Addition (+)
• Subtraction (-)
• Multiplication (*)
• Division (/)
• Modulus (%), which returns the remainder of a division operation
• Exponentiation (**), which raises a number to a specified power

Order of Operations:

In Python expression, the order of operations follows the standard order of operations, also known as PEMDAS (Parentheses, Exponentiation, Multiplication and Division, and Addition and Subtraction). This means that operations inside parentheses are performed first, followed by exponentiation, then multiplication and division, and finally addition and subtraction.

Example:
Here are some examples of arithmetic Expressions-

Example 1
Let’s have a look at the below example of an arithmetic expression which is using multiple operators in one expression.

Code Implementation:

x = 2 + 3 * 4 - 5 / 2 ** 3
result = x
print(result)
# Output: 13.6875

Output:

13.375

Explanation:
We solved it using the BODMASS rule or with the help of the order of operations.

Example 2
Below we will see an example of arithmetic expression which is using the % operator –

Code Implementation:

a = 10
b = 3
c = a % b
result = c
print(result)
# Output: 1

Output:

1

Explanation:
In this example, the modulus operator is used to find the remainder of the division of a and b, which is 1. Then the result is stored in the variable c and printed.

Example 3-
In this third example of arithmetic expression we are using the ** operator which means power –

Code Implementation:

x = 2
y = 5
z = x ** y
result = z
print(result)
# Output: 32

Output:

32

Explanation:
In this example, the exponentiation operator (**) is used to raise the value of x to the power of y, which is 2 raised to the power of 5, resulting in 32. Then the result is stored in the variable z and printed.

Comparison Expression in Python:

In Python expression, comparison expressions are used to compare the value of two or more variables. These expressions return a Boolean value of either True or False, which can be used to control the flow of a program. Comparison expressions are often used in conjunction with control flow statements such as if-else and while loops, as well as in conjunction with other comparison and logical operators.

Types of Operators:

Python provides a variety of operators that can be used in comparison expressions. These operators include:

• Less than (<)
• Greater than (>)
• Less than or equal to (<=)
• Greater than or equal to (>=)
• Equal to (==)
• Not equal to (!=)
• Identity operator (is)
• Membership operator (in)

Evaluation of Comparison Expressions:
When a comparison expression is evaluated, the values of the operands are compared, and the result of the comparison is returned as either True or False. For example, if the expression "5 < 10" is evaluated, the result would be True, as 5 is less than 10.

Examples:
Here are some examples of comparison Expression-

Example 1-
In this example, we will use < operator to make a comparison Expression –

Code Implementation:

x = 5
y = 10
result = x < y
print(result)
# Output: True

Output:

True

Explanation:
In this example, the less than operator (<) is used to compare the value of x and y. Since 5 is less than 10, the comparison returns True and the result is printed.

Example 2-
Below is the example of is operator –

Code Implementation:

a = [1,2,3,4]
b = [1,2,3,4]
result = a is b
print(result)
# Output: False

Output:

False

Explanation:
In this example, the identity operator (is) is used to compare the identity of a and b, which are two different lists with the same elements. The comparison returns False and the result is printed.

Logical Expression in Python:

In Python, logical expressions are used to combine comparison expressions and other logical expressions. These expressions return a Boolean value of either True or False, which can be used to control the flow of a program. Logical expressions are often used in conjunction with control flow statements such as if-else and while loops, as well as in conjunction with other comparison and logical operators.

Types of Operators:
Python provides a variety of operators that can be used in logical expressions. These operators include:

• Logical AND (and)
• Logical OR (or)
• Logical NOT (not)

Evaluation of Logical Expression in Python:
When a logical expression is evaluated, the values of the operands are compared, and the result of the comparison is returned as either True or False. For example, if the expression "5 < 10 and 3 > 1" is evaluated, the result would be True, as both comparisons in the expression are true.

Example:
Let’s look at the example which will use or operator-

Code Implementation:

a = "hello"
b = "world"
result = a != b or len(a) > 3
print(result)
# Output: True

Output:

True

Explanation:
In this example, the logical or operator (or) is used to combine the comparison expressions "a != b" and "len(a) > 3". The first comparison is true, so the expression returns True and the result is printed.

Multiple Operators in Python Expression (Operator Precedence):

In Python expression, expressions can contain multiple operators. These operators may include mathematical operators such as +, -, *, and /, as well as comparison operators such as >, <, >=, <=, ==, and !=, and logical operators such as and, or, and not. When multiple operators are used in an expression, it is important to understand the rules for operator precedence, which determine the order in which the operators are applied.In this example, the expression x > 3 is used in the if statement to determine which branch of the statement to execute.

Operator Precedence:

Python expression follows a set of rules for determining the order in which operators are applied in an expression. These rules, known as operator precedence, dictate that some operators are applied before others. For example, the multiplication operator () has higher precedence than the addition operator (+), so in the expression 2 + 3 4, the multiplication operator is applied first and the result is 12.

Here is the precedence order of different operators in python:

• Parentheses ()
• Exponentiation **
• Unary + and –
• Multiplication, Division, Floor division, Modulus *, /, //, %
• Addition, Subtraction +, –
• Left and Right shift
• Bitwise AND &
• Bitwise XOR ^
• Bitwise OR |
• Comparison operators <, >, <=, >=, ==, !=
• Logical NOT not
• Logical AND and
• Logical OR or

Example –
Here is an example of an expression that uses multiple operators with different precedence:

x = (2 + 3) * 4 - 5 / 2

In this expression, the parentheses have the highest precedence, so the addition of 2 and 3 is done first and returns 5. Next, the multiplication of 5 and 4 is done and returns 20. Then the division of 5 by 2 is done and returns 2.5.
Finally, 20-2.5=17.5

If we didn’t use the parentheses, the order of operation would have been different and the output would have been different.

x = 2 + 3 * 4 - 5 / 2

In this expression, the multiplication of 3 and 4 is done first and returns 12. Then the addition of 2 and 12 is done and returns 14. Next, the division of 5 by 2 is done and returns 2.5. Finally, 14 – 2.5 = 11.5

Difference between Statements and Expression in Python:

Statements and expressions are both used in Python, but they serve different purposes.

Statements:
Statements are used to perform actions or change the state of the program. They are used to execute code and do not return a value. Examples of statements include assignment statements, function calls, and control statements.

For example, in the following statement, the variable x is assigned the value 5:
x = 5

Expressions:
Expressions are used to evaluate to a single value. They can be used in a variety of ways, such as in assignment statements, function arguments, and conditional statements. Expressions return a value and are often used to compute a value and assign it to a variable.

For example, in the following expression, the values 2 and 3 are added together and the result is stored in the variable x:
x = 2 + 3

Usage:
Statements are used to execute code and control the flow of the program, while expressions are used to compute a value. Expressions can be used in statements, but statements cannot be used in expressions.

For example, the following is a statement that uses an expression:

x = 2 + 3

The following, on the other hand, is an expression that uses a statement:

(x = 2) + 3

This will raise a syntax error because statements cannot be used in expressions.

Combination:
Statements and expressions can be combined to create more complex code. For example, a control statement such as an if-else statement can use expressions to evaluate the conditions:

if x > 3:
print("x is greater than 3")
else:
print("x is not greater than 3")

In this example, the expression x > 3 is used in the if statement to determine which branch of the statement to execute.

Hence, Statements and expressions are both important components of programming in Python. Understanding the difference between the two and how they are used is essential for writing efficient and effective code. While statements are used to execute code and control the flow of the program, expressions are used to compute a value. By using them together, programmers can create powerful and complex programs.

Summary
In this article, we have discussed the importance and different types of Expression in Python. We have also discussed the use of multiple operators in expressions and how Python follows a set of rules for determining the order in which operators are applied in an expression, known as operator precedence. We have also highlighted the difference between statements and expression in Python.