An expression is defined as a combination of constants, variables, and operators . An expression always evaluates to a value . A value or a standalone variable is also considered as an expression but a standalone operator is not an expression.
Examples of expressions in python:
- 125
- n
- n - 25
- 25 + 67
- “abc” + “def”
Precedence of Operators
- Evaluation of the expression is based on precedence of operators.
- When an expression contains different kinds of operators, precedence determines which operator should be applied first.
- Higher precedence operator is evaluated before the lower precedence operator.
- Unary operators need only one operand, and they have a higher precedence than the binary operators.
- Parenthesis can be used to override the precedence of operators. The expression within () is evaluated first.
- For operators with equal precedence, the expression is evaluated from left to right.
Examples:
1. 30 + 40 * 2
Step 1: 30 + (40*2)
Step 2: 30 + 80
Answer: 110
2. 20 - 30 + 50
Step 1: (20-30) + 50
Step 2: -10 + 50
Answer: 40