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.

Order of Precedence of Operators - Teachoo.jpg

 

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

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Davneet Singh's photo - Co-founder, Teachoo

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Davneet Singh

Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 14 years. He provides courses for Maths, Science and Computer Science at Teachoo