Operator precedence and evaluation order in Python - Step-by-Step Execution

Concept Flow - Operator precedence and evaluation order

Start Expression

↓

Identify Operators

↓

Check Precedence

↓

Evaluate Highest Precedence Operator

↓

Replace Result in Expression

↓

More Operators?

Yes→Repeat Check Precedence

No↓

Final Result

The program looks at the expression, finds the operator with the highest priority, evaluates it first, replaces it with the result, and repeats until done.

Execution Sample

Python

result = 3 + 4 * 2
print(result)

Calculates 3 plus 4 times 2, showing how multiplication happens before addition.

Execution Table

Step	Expression	Operator Evaluated	Operation	Intermediate Result
1	3 + 4 * 2	*	4 * 2	8
2	3 + 8	+	3 + 8	11
3	11	None	None	11

💡 No more operators left, final result is 11

Variable Tracker

Variable	Start	After Step 1	After Step 2	Final
result	undefined	undefined	11	11

Key Moments - 3 Insights

Why does multiplication happen before addition in the expression?

Because multiplication has higher precedence than addition, as shown in step 1 of the execution_table where 4 * 2 is evaluated first.

What if we want addition to happen first?

We can use parentheses to change order, like (3 + 4) * 2, which forces addition before multiplication.

Does evaluation always go left to right?

No, operators with higher precedence are evaluated first regardless of position, but operators with the same precedence are evaluated left to right.

Visual Quiz - 3 Questions

Look at the execution_table, what is the intermediate result after evaluating the first operator?

A 11

B 8

C 6

D None

💡 Hint

Check the 'Intermediate Result' column in step 1 of the execution_table.

At which step does the addition operator get evaluated?

A Step 1

B Step 3

C Step 2

D Never

💡 Hint

Look at the 'Operator Evaluated' column in the execution_table.

If the expression was changed to (3 + 4) * 2, what would be the first operator evaluated?

A Addition (+)

B Multiplication (*)

C None

D Both at the same time

💡 Hint

Parentheses change evaluation order; check key_moments about parentheses.

Concept Snapshot

Operator precedence decides which part of an expression runs first.
Multiplication and division have higher precedence than addition and subtraction.
Use parentheses () to change the order.
Operators with the same precedence run left to right.
Python evaluates expressions step-by-step following these rules.

Full Transcript

This lesson shows how Python decides which part of a math expression to calculate first. It looks at the operators and their priority. For example, multiplication happens before addition. We traced the expression 3 + 4 * 2. First, 4 times 2 equals 8. Then 3 plus 8 equals 11. We also learned that parentheses can change this order. Operators with the same priority are done left to right. This helps us understand how Python calculates results step by step.