# ---------- FUNCTION BASICS ----------

# Functions allow use to reuse code and make the code easier

# to understand

# To create a function type def (define) the function name

# and then in parentheses a comma separated list of values

# to pass if needed

def add_numbers(num_1, num2):

# Return returns a value if needed

return num_1 + num2

# You call the function by name followed by passing comma

# separated values if needed and a value may or may not be

# returned

print("5 + 4 =", add_numbers(5, 4))

# ---------- FUNCTION LOCAL VARIABLES ----------

# Any variable defined inside of a function is available only

# in that function

# ---------- EXAMPLE 1 ----------

# Variables created in a function can't be accessed outside

# of it

def assign_name():

name = "Doug"

assign_name()

# Throws a NameError

# print(name)

# ---------- EXAMPLE 2 ----------

# You can't change a global variable even if it is passed

# into a function

def change_name(name):

# Trying to change the global

name = "Mark"

# A variable defined outside of a function can't be changed

# in the function using the above way

name = "Tom"

# Try to change the value

change_name(name)

# Prints Tom even though the function tries to change it

print(name)

# ---------- EXAMPLE 3 ----------

# If you want to change the value pass it back

def change_name_2():

return "Mark"

name = change_name_2()

print(name)

# ---------- EXAMPLE 4 ----------

# You can also use the global statement to change it

gbl_name = "Sally"

def change_name_3():

global gbl_name

gbl_name = "Sammy"

change_name_3()

print(gbl_name)

# ---------- RETURNING NONE ----------

# If you don't return a value a function will return None

def get_sum(num1, num2):

sum = num1 + num2

print(get_sum(5, 4))

# ---------- PROBLEM : SOLVE FOR X ----------

# Make a function that receives an algebraic equation like

# x + 4 = 9 and solve for x

# x will always be the 1st value received and you only

# will deal with addition

# Receive the string and split the string into variables

def solve_eq(equation):

x, add, num1, equal, num2 = equation.split()

# Convert the strings into ints

num1, num2 = int(num1), int(num2)

# Convert the result into a string and join (concatenate)

# it to the string "x = "

return "x = " + str(num2 - num1)

print(solve_eq("x + 4 = 9"))

# ---------- RETURN MULTIPLE VALUES ----------

# You can return multiple values with the return statement

def mult_divide(num1, num2):

return (num1 * num2), (num1 / num2)

mult, divide = mult_divide(5, 4)

print("5 * 4 =", mult)

print("5 / 4 =", divide)

# ---------- RETURN A LIST OF PRIMES ----------

# A prime can only be divided by 1 and itself

# 5 is prime because 1 and 5 are its only positive factors

# 6 is a composite because it is divisible by 1, 2, 3 and 6

# We'll receive a request for primes up to the input value

# We'll then use a for loop and check if modulus == 0 for

# every value up to the number to check

# If modulus == 0 that means the number isn't prime

def isprime(num):

# This for loop cycles through primes from 2 to

# the value to check

for i in range(2, num):

# If any division has no remainder we know it

# isn't a prime number

if (num % i) == 0:

return False

return True

def getPrimes(max_number):

# Create a list to hold primes

list_of_primes = []

# This for loop cycles through primes from 2 to

# the maximum value requested

for num1 in range(2, max_number):

if isprime(num1):

list_of_primes.append(num1)

return list_of_primes

max_num_to_check = int(input("Search for Primes up to : "))

list_of_primes = getPrimes(max_num_to_check)

for prime in list_of_primes:

print(prime)

# ---------- UNKNOWN NUMBER OF ARGUMENTS ----------

# We can receive an unknown number of arguments using

# the splat (*) operator

def sumAll(*args):

sum = 0

for i in args:

sum += i

return sum

print("Sum :", sumAll(1,2,3,4))

# ---------- pythontut2.py ----------

# We need this module for our program

import math

# Functions allow us to avoid duplicate code in our programs

# Aside from having to type code twice duplicate code is bad

# because it requires us to change multiple blocks of code

# if we need to make a change

# ---------- OUR FUNCTIONS ----------

# This routes to the correct area function

# The name of the value passed doesn't have to match

def get_area(shape):

# Switch to lowercase for easy comparison

shape = shape.lower()

if shape == "rectangle":

rectangle_area()

elif shape == "circle":

circle_area()

else:

print("Please enter rectangle or circle")

# Create function that calculates the rectangle area

def rectangle_area():

length = float(input("Enter the length : "))

width = float(input("Enter the width : "))

area = length * width

print("The area of the rectangle is", area)

# Create function that calculates the circle area

def circle_area():

radius = float(input("Enter the radius : "))

area = math.pi * (math.pow(radius, 2))

# Format the output to 2 decimal places

print("The area of the circle is {:.2f}".format(area))

# ---------- END OF OUR FUNCTIONS ----------

# We often place our main programming logic in a function called main

# We create it this way

def main():

# Our program will calculate the area for rectangles or circles

# Without functions we'd have to create a giant list of ifs, elifs

# Ask the user what shape they have

shape_type = input("Get area for what shape : ")

# Call a function that will route to the correct function

get_area(shape_type)

# Because of functions it is very easy to see what is happening

# For more detail just refer to the very short specific functions

# All of the function definitions are ignored and this calls for main()

# to execute when the program starts

main()

# ---------- HOMEWORK ----------

# Add the ability to calculate the area for parallelograms,

# rhombus, triangles, and trapezoids