#!/usr/bin/env python
# coding: utf-8

# In[4]:


# Section 5.2 continued
# Can define multiple functions in the same program 
# no problem!
def main():
    print("This is my program.")
    message()
    print("Bye!")

def message():
    print("Hello")
    print("World!")

main()


# In[12]:


# Section 5.3 -- designing with functions
# first thing is a flowchart for the previous program
# we put this on the board
#
# Example program: a dryer company hires you to write a
# step-by-step evaluation program for fixing dryers of
# a certain brand. The steps they want are as follows:
# Step 1. Unplug and move the dryer from the wall
# Step 2. Remove the six screws from the back.
# Step 3. Remove the back panel.
# Step 4. Pull top part straight out.
#
# requirements: each step to be displayed one at a time,
# and user should hit enter to proceed to the next step
#
# Goal here: write each step as a function and then 
# wrap those functions into an order.
def main():
    # display a welcome message and wait for user input
    start_message()
    input("Press enter to continue.")
    # display step 1 & wait
    step1()
    input("Press enter to continue.")
    # display step 2 and wait
    step2()
    input("Press enter to continue.")
    # display step 3 and wait
    step3()
    input("Press enter to continue.")
    # display step 4 and wait
    step4()

def start_message():
    print("Welcome to the repair utility for the XR123 dryer.")
def step1():
    print("Unplug and move the dryer from the wall")
def step2():
    print("Remove the six screws from the back.")
def step3():
    print("Remove the back panel.")
def step4():
    print("Pull top part straight out.")

main()
print(type(main()))


# In[15]:


# Section 5.4 -- local variables
# Variables defined within a function cannot be retrieved
# from outside of the function. 
#
# Essentially -- variables are destroyed when a function
# completes its steps. 
#
# The following example illustrates the point:
def main():
    get_name()
    print("Hello for the second time",name)
def get_name():
    # define variable name and get input from user for it
    name=input("Enter your name!")
    print("Hello for the first time",name)
main()

# notice in the above code that the "Hello for the first time"
# print command works as expected -- its printed the user
# inserted name without problem. HOWEVER, the "Hello for the
# second time" print command fails to work as expected --
# it gives an error!! 
#This is because the "name" variable is destroyed when the
# get_name() function is called and completes. So the 
# variable is not accessible except within that function's code.

# So we say that the variable "name" occurring in the get_name()
#function is a "local variable" -- it is "local" to the get_name()
# function. We say that this "name" variable is "in the scope"
# of the get_name() function. Here, "scope" is referring to
# the occurrence of it within that function's statements.


# In[29]:


# Bird example from the book
# The same variable is used in different functions without problem.
def main():
    texas()
    birds=5
    westvirginia()
    texas()
    westvirginia()
def texas():
    birds=10000
    print("There are",birds,"birds in Texas.")
def westvirginia():
    print("There are",birds,"birds in West Virginia.")
    # uncommenting the following line causes an error
    # because the interpreter thinks you made a mistake
#    birds=2000
main()


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