functions_notes_1_finished.py

"""
Name:
Title: Notes on Functions
Description: Notes on the basics of defining and using functions in Python.
"""

# A FUNCTION is a reusable block of code that performs a specific task.
#   Functions allow you to abstract away unnecessary information and leverage modular design.
#   Built-in functions we know: print(), input(), len(), random.randint(), etc.

#  ABSTRACTION is hiding all but the most relevant details.
#   Lets you think about the big picture without worrying about the details.
#   e.g. variable or function names are an abstraction of their actual contents.

# 1: Creating a function is referred to as... Defining a Function

# FUNCTION DEFINITION is the entire function, both header and body.
def hello_printer():  # FUNCTION HEADER is the first line of a function definition.
	print ("Hello, World.")  # FUNCTION BODY is the indented block of code below the header.

# 2: Using a function is referred to as... "calling a function" or a FUNCTION CALL

hello_printer()
hello_printer()
#hello_printer  # always need parentheses in a function call.
print(hello_printer())  # returns 'None'

# *** INSTRUCTOR'S NOTE: Do Peer Instruction #1 & #2 ***

# 3: DOCSTRING. A special way to document a function;
#    It must be triple quoted (single or double), and on the first line after the function header.
#    Can provide useful information when attempting to use the function.

def greeting():
	"""This will greet the user to a program"""
	print("\nWelcome to the program!\n")

greeting()
help(greeting) # help function is one way to see documentation for a function
help(len)

# 4: PARAMETERS: Variable names inside the parentheses of a
#      function header. A function receives a value through its
#      parameters. Parameters catch values sent to the function
#      from a function call.
#    ARGUMENTS: Values sent to a function to use. (put in parentheses of a
#      function call)
#   *note: These terms are sometimes used interchangeably, but we will stick to these strict definitions for this class.

def personal_greeting(name):   # message is a parameter
	"""Greets a person by name."""
	print("\nHello, " + name + "! Welcome to the program.\n")

personal_greeting("Jake") # the string "Jake" is an argument
personal_greeting("Class") # the string "Class" is an argument
name = input("Enter your name: ").title()
personal_greeting(name)  # the variable name is an argument

# NOTE... If I define a function with one parameter, then I must
#       use the same number of arguments when calling the function
#personal_greeting() # ERROR
# personal_greeting("Hi", "Jake") # ERROR

# 5: You can have multiple parameters:

def message(message, name):
	"""A message said by a person."""
	print(name + ":" , message)

message("Hello, class.", "Mr. Callaghan")  # arguments are accepted in positional order

# 6: RETURNING.  You can get value(s) out of a function by returning value(s).
#   A RETURN VALUE is a value received back from a function call.
#    You can return a value from a function by using
#    a RETURN STATEMENT. A function always ends after
#    executing a return statement, and the RETURN VALUE is returned.

def give_me_five():
	"""Returns the number five."""
	print("Here is your number 5!")
	return 5
	print("test") # unreachable code (function ends after the return statement)

number = give_me_five()
print ("Return value: ", number)

# A function can return any type of value, but only one value at a time
def give_me_ten():
	lefthand= 5
	righthand= 5
	return (lefthand, righthand) # tuple

return_value = give_me_ten()
number1, number2 = return_value # unpack tuple into its elements
print("Return value:", return_value)
print("Left", number1)
print("Right", number2)

# *** INSTRUCTOR'S NOTE: Show in Python Visualizer (Python Tutor) and Do Peer instrution #3 & #4 ***

# CHALLENGE: Can you define a function that can simulate
#           the rolling of two dies and return both values?
# CHALLENGE 2: Create a new function to add your two die rolls
#           together and return the total.

import random

# define all functions at the top of your program:
def dub_roll():
	'''Generates a double die roll and returns it as a tuple'''
	die1 = random.randint(1,6)
	die2 = random.randrange(1,7)
	return (die1, die2)

def add_2(num1, num2):
	'''adds two number together and returns the total'''
	total = num1 + num2
	return total

# use all functions below in your main code
roll1, roll2 = dub_roll()
roll3, roll4 = dub_roll()

print("The first roll is",roll1,"and the second is",roll2)
print("The first roll is",roll3,"and the second is",roll4)

tot = add_2(roll1, roll2)
tot2 = add_2(roll3, roll4)

print("\nThe total of rolls 1 & 2 is", tot)
print("\nThe total of rolls 3 & 4 is", tot2)

input("Press enter to exit.")