Operators in Python: Exploring Operator Precedence in Python

Introduction

Operator precedence in Python determines the order in which operators are evaluated in an expression. Operators with higher precedence are evaluated before operators with lower precedence. Operator precedence rules dictate how the expressions are evaluated, affecting the outcome of your code. Understanding operator precedence is crucial for writing correct and predictable code. In this article, we are going to explore the precedence of arithmetic, comparison, and logical operators in Python. We are going to use code examples to demonstrate the order in which operators are evaluated in an expression.

Arithmetic Operators

Here is an expression that demonstrates the operator precedence of arithmetic operators:

In this code, the multiplication (*) operator and the division operator (/) have equal precedence, which is higher than the addition and subtraction operators. If operators have equal precedence, the operator on the left is evaluated first. In this case, the multiplication operator is on the left, so (3 * 4) is evaluated first, which gives us 12. The division operator has higher precedence than the addition and subtraction operators, so (12/2) is evaluated next, which gives us 6. Now, the addition operator (+) and the subtraction operator (-) have equal precedence. Remember, the operator on the left is evaluated first. In this case, the subtraction operator (-) is on the left, so (15 minus 2) is evaluated, and we get 13. Next, the addition operator is evaluated, so we get (13 + 6), which gives us 19.0. We get a floating number output because the division operator (/) always returns a float number.

Now, let’s see what happens once we add parentheses() to the expression:

You can see that the answer has changed from 19.0 to 32.0. This is because operator precedence has changed. The parentheses () have the highest precedence, so the expression inside is evaluated first from left to right (15 – 2 + 3), which gives us 16. Then, we multiply 16 by 4 because the multiplication operator comes after the parentheses but before the division operator. This gives us 64. Next, we divide 64 by 2 to get 32.0.

Logical and Comparison Operators

Let’s look at comparison operators and two logical operators, the "or" operator and the "and" operator, by evaluating the code below:

In this code, comparison operators (==, <, >, >=, <=, !=, ==) have a higher precedence than the "and" and "or" operators. Since the comparison operators have equal precedence, the expression on the left will be evaluated first. In this case, "x==3" is evaluated first. Since x is not equal to 3, this evaluates to False. Next in line is "x > 5." This evaluates to True because x is less than 5. The final expression is "y > 10," which evaluates to False since y is less than 10. So, we can summarize the resulting expression as: (False or True and False). Since the "and" operator has a higher precedence, (True and False) is evaluated first. This evaluates to False because one operand is False (the "and" operator will return True if both operands are True). The expression has now become (False or False), which evaluates to False because both operands are False. This means that the if statement evaluates to False. Because it is False, the else block is executed, and we get "You lose."

The "not" Operator

Let’s add the "not" operator to the expression above and evaluate the results:

The behavior of the "not" operator is that it flips or inverts the truth of an expression. If an expression is True, the "not" operator will make it False and vice versa.  The "not" operator has higher precedence than the "and" and "or" operators. So when the comparison operators are evaluated and we get the expression (not False or True and False), the "not" operator will flip the False operand (not False) to True. The resulting expression will be: (True or True and False). The "and" operator is evaluated next (True and False), and we get False. The expression has now become (True or False). Since the "or" operator requires at least one operand to be True to evaluate to True, the expression (True or False) evaluates to True. This means that the if-statement evaluates to True, hence "You win" is executed.

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Conclusion

These examples demonstrate the importance of understanding operator precedence when writing code in Python. Operator precedence is a fundamental concept that ensures the proper execution of expressions, leading to correct and predictable results in your code. Thanks for reading this article. Please like, share, and subscribe to this newsletter if you are not yet a subscriber.