An expression is code that evaluates to a value. Expressions appear in assignments, arguments, comparisons, and many other places.
Understanding the Concept
Examples include 3 + 4, a variable name, or a function call that returns a value. Python evaluates operators according to rules such as multiplication before addition unless parentheses change the order. A statement is a broader unit of execution, such as an assignment or an if statement. Some statements contain expressions, but not every statement produces a value that can be used inside another expression.
When and Why You Would Use This
Compare two expressions. One evaluates arithmetic and another evaluates a comparison, producing a Boolean result. We will discuss these operators in dedicated lessons later.
Practical Example
calculation_result = (5 + 3) * 2
is_large = calculation_result > 10
print(calculation_result)
print(is_large)Understanding the Example
The arithmetic expression evaluates to 16. The comparison evaluates to True. Both results are assigned and then printed. The parentheses ensure the addition happens before multiplication.
Example Output
16
TrueTry It Yourself
Predict the output of 2 + 3 * 4 and (2 + 3) * 4; then test both expressions.
Common Beginner Mistakes
- Assuming every statement produces a value that can be assigned.
- Ignoring operator precedence when predicting expressions.
- Confusing a Boolean comparison result with the number being compared.
Key Takeaways
- Expressions evaluate to values.
- Assignments can store expression results under names.
- Parentheses make evaluation order explicit.