less1and2

# Udacity Introduction to Computer Science Class
# Notes and snippets - all in Python
#Fall 2016

#####################################
#Lesson One
# Variables Quiz
# Given the variables defined here, write Python 
# code that prints out the distance, in meters, 
# that light travels in one processor cycle. 

# speed_of_light in meters per second
# cycles_per_second is 2.7 GHz

speed_of_light = 299792458.0 
cycles_per_second = 2700000000.0
print speed_of_light / cycles_per_second
########################################
#Spirit Age Quiz
# Write python code that defines the variable 
# age to be your age in years, and then prints 
# out the number of days you have been alive.

age = 45

print (age / 4) + (age * 365)
#####################################
#Quiz Capital Udacity
# Write Python code that prints out Udacity (with a capital U), 
# given the definition of s below.

s = 'audacity'

print str.capitalize(s[1:8])
#print str.upper (s [1:2])
#print str.lower (s[2:8 ])
#######################################
#Quiz Extracting Links
# Write Python code that initializes the variable
# start_link to be the value of the position
# where the first '<a href=' occurs in a page.

page = '''<div id="top_bin"> <div id="top_content" class="width960">
   <div class="udacity float-left"> <a href="/">'''

start_link = page.find
######################################
#Lesson One Final Quiz
# Write Python code that assigns to the 
# variable url a string that is the value 
# of the first URL that appears in a link 
# tag in the string page.
# Your code should print http://udacity.com
# Make sure that if page were changed to

#page = '<a href="http://udacity.com">Hello world</a>'

# that your code still assigns the same value to the variable 'url', 
# and therefore still prints the same thing.

# page = contents of a web page
page =('<div id="top_bin"><div id="top_content" class="width960">'
'<div class="udacity float-left"><a href="http://udacity.com">')
start_link = page.find('<a href=')
end_link=page.find('>',start_link)-1
start_url = start_link + 9

url = page[start_url:end_link]

print url


############################################
# Lesson One - Text Replacement Quiz
###############################################
#       Exercise by Websten from forums       #
###############################################
# To minimize errors when writing long texts with
# complicated expressions you could replace 
# the tricky parts with a marker. 
# Write a program that takes a line of text and 
# finds the first occurrence of a certain marker 
# and replaces it with a replacement text. 
# The resulting line of text should be stored in a variable. 
# All input data will be given as variables.
#
# Replace the first occurrence of marker in the line below.
# There will be at least one occurrence of the marker in the
# line of text. Put the answer in the variable 'replaced'.
# Hint: You can find out the length of a string by command
# len(string). We might test your code with different markers!

# Example 1
marker = "AFK"
replacement = "away from keyboard"
line = "I will now go to sleep and be AFK until lunch time tomorrow."

# Example 2 # uncomment this to test with different input
#marker = "EY"
#replacement = "Eyjafjallajokull"
#line = "The eruption of the volcano EY in 2010 disrupted air travel in Europe for 6 days."

###
# YOUR CODE BELOW. DO NOT DELETE THIS LINE
###

replaced =

print replaced
# Example 1 output should be:
#>>> I will now go to sleep and be away from keyboard until lunch time tomorrow.
# Example 2 output should be:
#>>> The eruption of the volcano Eyjafjallajokull in 2010 disrupted air travel in Europe for 6 days.

#######################################
#Lesson One - Palindrome Problem 
###############################################
#       Exercise by Websten from forums       #
###############################################
# A palindrome is a word or a phrase that reads 
# the same backwards as forwards. Make a program 
# that checks if a word is a palindrome. 
# If the word is a palindrome, print 0 to the terminal,
# -1 otherwise. 
# The word contains lowercase letters a-z and 
# will be at least one character long.
#
### HINT! ###
# You can read a string backwards with the following syntax:
# string[::-1] - where the "-1" means one step back.
# This exercise can be solved with only unit 1 knowledge
# (no loops or conditions)

#word = "madam"
# test case 2
word = "madman" # uncomment this to test

###
# YOUR CODE HERE. DO NOT DELETE THIS LINE OR ADD A word DEFINITION BELOW IT.
###
bw_word=word[::-1]

is_palindrome =bw_word.find(word)

# TESTING
print is_palindrome
# >>> 0  # outcome if word == "madam"
# >>> -1 # outcome if word == "madman"

############################################
#Lesson Two

#Quiz - Square

# Define a procedure, square, that takes one number 
# as its input, and returns the square of that 
# number (result of multiplying
# the number by itself).
# To help you out, the code for sum(a,b) is below.

def sum(a,b):
    c = a + b
    return c

def square(n):
    n2 = n*n
    return n2


# To test your procedure, uncomment the print 
# statement below, by removing the hash mark (#) 
# at the beginning of the line.

# Do not remove the # from in front of the line 
# with the arrows (>>>). Lines which begin like 
# this (#>>>) are included to show the results
# you should see when run your procedure.

print square(5)
#>>> 25
######################
#Quiz Sum of Three
# Define a procedure, sum3, that takes three
# inputs, and returns the sum of the three
# input numbers.
# To help you out, the code for sum(a,b) is below.

def sum(a,b):
    return a + b

def sum3(a,b,c):
    return a+b+c





print sum3(1,2,3)
#>>> 6

print sum3(93,53,70)
#>>> 216

##############################
# Define a procedure, abbaize, that takes
# two strings as its inputs, and returns
# a string that is the first input,
# followed by two repetitions of the second input,
# followed by the first input.


def abbaize(a,b):
    return a+b+b+a






print abbaize('a','b')
#>>> 'abba'

print abbaize('dog','cat')
#>>> 'dogcatcatdog'

###############################
# Quiz Find Second
# Define a procedure, find_second, that takes
# two strings as its inputs: a search string
# and a target string. It should return a
# number that is the position of the second
# occurrence of the target string in the
# search string.

def find_second (search,target):
    first=search.find(target)
    return search.find (target,first+1)
    
danton = "De l'audace, encore de l'audace, toujours de l'audace"
print find_second(danton, 'audace')
#>>> 25

twister = "she sells seashells by the seashore"
print find_second(twister,'she')
#>>> 13

###################
#Quiz If Statements

# Define a procedure, bigger, that takes in
# two numbers as inputs, and returns the
# greater of the two inputs.


def bigger(a,b):
    if a==b:
        return a
    if a>b:
        return a
    if b>a:
        return b




print bigger(2,7)
#>>> 7

print bigger(3,2)
#>>> 3

print bigger(3,3)
#>>> 3

######################
#Quiz Is Friend
# Define a procedure, is_friend, that
# takes a string as its input, and
# returns a Boolean indicating if
# the input string is the name of
# a friend. Assume I am friends with
# everyone whose name starts with D
# and no one else. You do not need to
# check for the lower case 'd'

# below code prints d as answer
#s='diane'
#f=s[0]
#print f

def is_friend(s):
    friend='D'
    return s[0]==friend

print is_friend('Diane')
#>>> True

print is_friend('Fred')
#>>> False

##### if syntax example below
#def bigger(a,b):
#    if a==b:
#        return a
#    if a>b:
#        return a
#    if b>a:
#        return b

##########################
#Quiz More Friends
# Define a procedure, is_friend, that takes
# a string as its input, and returns a
# Boolean indicating if the input string
# is the name of a friend. Assume
# I am friends with everyone whose name
# starts with either 'D' or 'N', but no one
# else. You do not need to check for
# lower case 'd' or 'n'

def is_friend(name):
    friend='D'
    friend2='N'
    return name[0]==friend or name[0]==friend2



print is_friend('Diane')
#>>> True

print is_friend('Ned')
#>>> True

print is_friend('Moe')
#>>> False

#############################
#Quiz Print Numbers
# Define a procedure, print_numbers, that takes
# as input a positive whole number, and prints 
# out all the whole numbers from 1 to the input
# number.

# Make sure your procedure prints "upwards", so
# from 1 up to the input number.

#WRONG WORKING CODE BELOW - MUST PRINT NUMBERS SMALLEST TO LARGEST
def print_numbers(a):
    while a != 0:
        print a
        a=a-1
    
print_numbers(3)
#>>> 1
#>>> 2
#>>> 3

#CORRECT WORKING CODE BELOW
def print_numbers(a):
    b=0
    while b != a:
        b=b+1
        print b

#PROF ANSWER BELOW    
def print_numbers(n):
     i=1
     while i <= n
         print i
         i = i + 1

print_numbers(3)
#>>> 1
#>>> 2
#>>> 3
#####################################
#Quiz Factorial ERROR A:  Answer all is 1
#def factorial(n):
#    i=1
#    a=1
#    b=1
#    while i > 1:
#        i=n-1
#        a=n(i)
#        b=a*b
#    return b
       
#print factorial(4)
#>>> 24  err 1
#print factorial(5)
#>>> 120 err 1
#print factorial(6)
#>>> 720 err 1

#ERROR B:  Answer to all is None
#def factorial(n):
#    i=1
#    a=1
#    n=1
#    while i > 1:
#        i=n-1
#        a=n*i
#        b=a+b
#        return b
#ERROR C:  Answer to all is zero 0        
#def factorial(n):
#    i=1
#    a=1
#    n=1
#    b=0
#    while i >= 1:
#        i=n-1
#        a=n*i
#        b=a+b
#    return b
      
#ERROR D:  Infinite loop
#def factorial(n):
#    i=1
#    a=1
#    b=0
#    while i >= 1:
#        i=n-1
#        a=n*i
#        b=a+b
#    return b
    
#CORRECT ANSWER!  YAY!
def factorial(n):
    b=1
    while n >= 1:
        b=b*n
        n=n-1
    return b
            

print factorial(4)
#>>> 24
print factorial(5)
#>>> 120
print factorial(6)
#>>> 720

## Break Quiz
# Use this to try out anything you like. Use print to display your answer
# when you press the "Test Run" button.
# Use the "Reset" button to reset the screen 

#While <T>
# <S>

#<T>
#countdown >= 0:

#<S>
#print countdown
#countdown = countdown - 1

#while True:
#    print 'Hello'

#<code>
#while True:
#    print 'Hello'
#    while True:
#        break
#    print 'Goodbye'
#    break
#</code>
#which codes has same results as the following for countdown?
def countdown(T):
#    while T >= 0:
#        print T
#        T = T - 1

#same#
#    while T>=0:
#        if False: 
#            break
#        print T
#        T = T-1

#diff#
#    while True:
#        print T
#        break

#diff#
#    while True:
#        if T:
#            break
#        print T
#        T=T-1
    
#same#    
#    while T:
#        print T
#        T=T-1
#        if T:
#            print T
#            T=T-1
#        else:
#            break


#######No links quiz

def get_next_target(page):
   start_link=page.find('<a href=')
   if start_link == -1:
      return None, 0
   start_quote = page.find('"', start_link)
   end_quote = page.find('"', start_quote + 1)
   url = page[start_quote + 1:end_quote]
   return url, end_quote
   
url, endpos = get_next_target('<div class="udacity float-left"><a href="http://udacity.com">')
if url:
   print "Here!"
else:
   print "Not Here!"
   
###### Print All Links

def print_all_links(page):
   while True:
      url, endpos = get_next_target(page)
      if url:
         print url
         page = page[endpos:]
      else:
         break
        
print_all_links(get_page('http://xkcd.com/353'))

#####Find_last##
# Define a procedure, find_last, that takes as input
# two strings, a search string and a target string,
# and returns the last position in the search string
# where the target string appears, or -1 if there
# are no occurrences.
#
# Example: find_last('aaaa', 'a') returns 3

# Make sure your procedure has a return statement.

def find_last(s,t):   
    last_point = -1
    while s.find(t) != -1:
        find_point = s.find(t,last_point+1)
        if find_point == -1:
            return last_point
        last_point = find_point
    return last_point

print find_last('aaaa','a')
#>>> 3

print find_last('aaaaa', 'aa')
#>>> 3

print find_last('aaaa', 'b')
#>>> -1

print find_last("111111111", "1")
#>>> 8

print find_last("222222222", "")
#>>> 9

print find_last("", "3")
#>>> -1

print find_last("", "")
#>>> 0