Lecture Notes on Python Math Module and Fruitful Functions (CPSC 121, Fall 2011), Study notes of Computer Science

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Today’s Topics ...

• Math module
• Fruitful functions

Homework

• HW 4 due
• HW 5 out

The math module

The math module contains many often used mathematical functions

import math help(math) # to browse functions available math.ceil(3.9999) # round up to next highest int 4 math.floor(3.9999) # round down to next lowest int 3 math.hypot(3, 4) # square root of a2 + b

math.log10(100) # the log base 10

math.log(16, 2) # the log base 2

math.sqrt(25) # the square root

• and so on ...
• The math module also includes math.pi and math.e constants

To round a float, use the built-in round function

round(3.2) 3 round(3.6) 4

When importing modules ...

• Function calls are prefixed with module name
• E.g., math.sqrt(25) instead of just sqrt(25)
• Can use “from math import *” instead to avoid this

Void functions actually return the special None value

result = print("Hi") Hi print(result) None type(result) <type ’NoneType’>

Defining fruitful functions

Return values using the return keyword

def succ(x): x = x + 1 return x

succ(1) 2 y = succ(2) print(y) 3

• A function can return at most one value
• A return statement can occur anywhere in the function

... but no statements after it is called will be executed

Q: What is returned?

z = 1 def f(x, y, z): result = x + y return result new_result = result + z return new_result