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Variables and Expressions, continued CMSC 201 Expressions Anything on the right hand side of the equals is an expression. Expressions can be anything that yields a value. a=4 b = 10 * a c = (100 * 4) / 9 + 2 d = sin(40) # This is a function call, which we’ll # discuss later. Operators So what can we do in python? Here are some basic operators: Operation Python Operator Addition + Subtraction - Multiplication * Division / Exponentiation ** Modulus % Operators Exponentiation: number ** power So if we want 3 squared, we say: 3 ** 2 If we want 2 cubed, it would be: 2 ** 3 Modulus Modulus: a%b Is equivalent to “the remainder of a after a is divided by b” 14 % 6 = 2 12 % 2 = 0 10 % 3 = 1 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 27th is. All you need to do is figure out 27 % 7, and that’s how many days past Monday you are. 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! 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! Other Math Functions Using “import math” we can access other math functions, such as: Function Purpose 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 pi The value of pi E The value of e