Some Examples

Some Examples
	Chapter 9. Functions

Here's a big example of using the odd, spinWheel and report functions.

Example 9.1. functions.py

#!/usr/bin/env python
import random

def odd( spin ):
    """odd(number) -> boolean."""
    return spin%2 == 1
    
def report( spin ):
    """Reports the current spin on standard output.  Spin is a String"""
    if int(spin) == 0:
        print "zero"
        return
    if odd(int(spin)):
        print spin, "odd"
        return
    print spin, "even"
    
def spinWheel():
    """Returns a string result from a roulette wheel spin."""
    t= random.randrange(38)
    if t == 37:
        return "00"
    return str(t)
    
for i in range(12):
    n= spinWheel()
    report( n )

	We've defined a function named `odd`. This function evaluates a simple expression; it returns `True` if the value of it's parameter, `spin`, is odd.
	The function called `report` uses the `odd` function to print a line that describes the value of the parameter, `spin`. Note that the parameter is private to the function, so this use of the variable name `spin` is technically distinct from the use in the `odd` function. However, since the `report` function provides the value of `spin` to the `odd` function, their two variables often happen to have the same value.
	The `spinWheel` function creates a random number and returns the value as a string.
	The “main” part of this program is the for loop at the bottom, which calls `spinWheel`, and then `report`. The `spinWheel` function uses `random.randrange`; the `report` function uses the `odd` function. This generates and reports on a dozen spins of the wheel. For most of our exercises, this free-floating main script is acceptable. When we cover modules, in Part IV, “Components, Modules and Packages”, we'll need to change our approach slightly to something like the following. def main(): for i in range(12): n= spinWheel() report( n ) main() This makes the main operation of the script clear by packaging it as a function. Then the only free-floating statement in the script is the call to `main`.


Function Varieties		Hacking Mode