# Lesson2

# Go over practice problems!

# Printing tricks:
  # Concationation: using the "+" to print out multiple things that have the same data type
  # Printing multiple things with different data types, seperate the pieces of data with commas

# EXAMPLE
print "A week has", 7, "days."


# Basic Arithmetic Functions
# + addition
# - subtraction
# * multiplication
# / integer division (gives the whole number division)
# % modulo (gives the remainder of divison)
# ** exponent/power


# CONCEPT 1: What is a program?
  # A program is a list of instructions for the
  # computer to execute in sequential order.
    # The instructions are written line by line in
    # the source code file. In python, our source
    # code files have the extension .py

# CONCEPT 2: How do I solve a problem computationally?
  # 1. Break down problem into smaller problems
  # 2. Make series of steps (e.g. algorithm)
    # to solve smaller problems.
  # 3. Write algorithm steps in English (pseudo-code)
  # 4. Write algorithm steps in real code
  # 5. Run code - your problem is (hopefully) solved!

# EXAMPLE 1:

# Problem - introduce yourself to someone

# Breakdown problem into series of smaller (algorithm)
# steps written in pseudo-code
# 1) print a greeting
# 2) print a name
# 3) print an age

# Write algorithm is real code
#print "Hello!"
#print "My name is Gabrielle."
#print "I am 19 years old."

# EXAMPLE 2:

# Problem - Write a program which translates celsius
# temperatures to fahrenheit.

# Algorithm in pseudo-code
# 1) Get a temperature input in degrees celsius from the user.
# 2) Use our formula to calculate fahrenheit temperature.
# 3) Tell the user the temperature in degrees fahrenheit.

# Algorithm broken down into even simpler steps!
# 1a) Get input from user
# 1b) Evaluate input as number
# 1c) Save number into a variable
# 2a) Calculate fahrenheit temperature with given formula
# 2b) Save fahrenheit temperature into a variable
# 3a) Print message explaining our calculation
# 3b) Print value of fahrenheit variable




# ACTIVITY 1
  # Write an algorithm for making your favorite meal.
  # Remember to be specific!

# ACTIVITY 2
  # Write the definition for an algorithm in your own words.

# ACTIVITY 3
  # Try to break down this problem into smaller subproblems:
  # PROBLEM - Drinking a glass of milk.
  # The first step could be
    # 1. Get the milk out of the refrigerator.


# CHECK IN
  # 1. True or False: The output of an algorithm can change even
  # if you give it the same inputs every time.
  # 2. True or False: Pseudo code is runnable code.

# CONCEPT 3: Input, Process, Output (IPO)

# 1. Get input from user
# 2. Process input / do some calculations to it
# 3. Output final calculations or information to the user

# EXAMPLE
#celsius = eval(input("Enter a temperature in degrees celsius: "))
#fahrenheit = 9/5 * celsius + 32
#print("The temperature is", fahrenheit, "degrees Fahrenheit.")





# VARIABLES
# Variables are simply names created by you that are used to keep
# track of information in your program.
# Each variable has some value associated to it.
# Variables are created when they are first assigned values.
# The value associated to a variable can be updated to a new value
# when used in an expression.
# Variables must be declared before they can be used in expressions.

# EXAMPLE 1
# The "=" is used to assign vales to variables.
counter = 100          # An integer (non decimal)
miles   = 1000.0       # A float (decimal)
name    = "John"       # A string

print counter
print miles
print name

# EXAMPLE 2
# Changing what is inside a variable.
changing = 3
print changing

changing = 9
print changing

# EXAMPLE 3
# Assigning the value of a variable to be the value of another variable
red = 5
blue = 10
print (red, blue)

yellow = red
print (yellow, red, blue)

# EXAMPLE 4
# Python allows you to assign a single value to several variables simultaneously.
a = b = c = 1
# Here, the number 1 is assigned to the variables a, b, and c.

# EXAMPLE 5
# You can also assign multiple objects to multiple variables.
a, b, c = 1, 2, "John"
# Here, a = 1, b = 2, and c = “John”.



# Rules for variable names
# 1. Names can not start with a number.
# 2. There can be no spaces in the name, use _ instead.
# 3. Can't use any of these symbols :'",<>/?|\()!@#$%^&*~-+
# 4. It's considered best practice (PEP8) that the names are lowercase.
# 5. Variable names should not be Python reserved words like with or not.