1. Variables and Expressions, continued CMSC 201

2. Expressions Anything on the right hand side of an assignment is an expression. An expression is anything that yields a value. a = 4 b = 10 * a c = (100 * 4) // 9 + 2 # This is a function call, # which we’ll discuss later. d = sin(40)

3. Operators Some basic operators: OperationPython Operator Addition+ Subtraction- Multiplication* Division/ // Exponentiation** Modulus%

4. Operators Exponentiation: number ** power So if we want 3 squared, we say: 3 ** 2 If we want 2 cubed, it would be: 2 ** 3

5. Modulus Modulus: a % b gives “the remainder of a after a is divided by b” 14 % 6 == 2 12 % 2 == 0 10 % 3 == 1

6. Modulus Why is modulus useful? Tells us if one thing is divisible by another (if you mod a by b and get zero, b is divisible by a) Remainders are useful! Imagine you know the first of a month is a Monday, and you want to know what day the 27 th is. All you need to do is figure out 27 % 7, and that’s how many days past Monday you are.

7. Integers vs. Floats Data in python remembers what type it is. a = 4 a is an integer. b = 4.4 b is a float. Floats and integers act differently!

8. Integer vs. Float Division a = 7 b = 3 print(a/b) prints 2.33333333 a = 7 b = 3 print(a//b) prints 2

9. Integers vs. Floats When we divide a float and anything else, the result is a float. However, there is often rounding error. 7.0 / 3.0 2.3333333333333335 Be careful to never compare two floats after you have done division! What happens if you print this??? print(2.3333333333333333)

10. Other Math Functions Other math functions: from math import * FunctionPurpose cos(x), sin(x), tan(x)Trigonometric functions log(x, base)Logarithm of x with given base floor(x)Finds the closest integer less than or equal x ceil(x)Finds the closest integer greater than or equal to x sqrt(x)Finds the square root of x piThe value of pi eThe value of e