Lossless Compression using Huffman Coding AlgorithmEdit in new window bubble 




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 Python Syntax


    

  • 

    keyboardInputsstat_minus_1
    

      

    • # Text inputname = input("Enter your name:")
      • 

    • # Whole number inputage = int(input("Enter your age:"))
      • 

    • # Decimal number inputprice = float(input("Enter a price:"))
      • 

    

  • 

    computerOutputsstat_minus_1
    

      

    • # Output text
print("Hello World")
      • 

    • # Output text + variable (String)
print("Hello " + playerName)
      • 

    • # Output text + variable (Integer/Float)
score = 5
      print("Your score: " + str(score))
      • 

    • # Clear the screenimport os
      os.system("clear")
      • 	

    

  • 

    note_stack_addVariables and Arithmetic Operatorsstat_minus_1
    

      

    • # Initialising variables and constants of different data types:
score = 0
      
PI = 3.14
      
message = "Hello World"
      
soundOn = True
      • 

    • # Arithmetic Operators:
x = a + b  # Add
      
x = a – b    # Take away
      
x = a / b    # Divide
      
x = a * b    # Multiply
      
x = a ** 2    # to the power of
      
x = a // b        # Quotient DIV
      
x = a % b       # Remainder MOD

      
x += 1 # Increment x by 1
      
x -= 1 # Decrement x by 1
      
x *= 2 # Multiply x by 2
      
x /= 2 # Divide x by 2

      • 

    • # Rounding a number:
pi = 3.14159
      
pi2 = round(pi,2)
      
print("Pi rounded to two decimal places: " + str(pi2))   # 3.14

    

  • 

    arrow_splitSelection: if, elif, else...stat_minus_1
    

      

    • if numberOfLives == 0:
      
   print("Game Over!")

    • if numberOfLives == 0 or timer<=0:
      
   print("Game Over!")
        
else:
      
   print("Carry on playing!")

    • if number < 0:
      
   print("Negative Number")
      
elif number == 0:
      
   print("Zero")
      
else:
      
   print("Positive Number")

    • if number == 7:
      
   print("Seven")
      
elif number == 8:
      
   print("Eight")
      
elif number == 9:
      
   print("Nine")
      
else:
      
   print("Not seven, eight or nine")
      • 

    

  • 

    autorenewIteration: for loops & While loopsstat_minus_1
    

      

    • 
# For loop to count from 1 to 10      
for i in range(1,11):
      
   print(i)

    •   
# For loop to count in 5 from 0 to 100
for i in range(0,101,5):
      
   print(i)

    • 
# For loop to count down from 10 to 1 using a negative step      
for i in range(10,0,-1):
      
   print(i)

    • 
# Iterate through all the values of a list
days = ["Mon", "Tue", "Wed", "Thu", "Fri"]
      
for i in range(0,len(days)):
      
   print(days[i])

    • 
# Iterate through all the values of a list - Alternative approach
for day in days:
      
   print(day)

    • 
# Iterate through all the characters of a string
string = "Hello World"
      
for character in string:
      
   print(character)

    • 
# Using a while loop   
i=0
      
while i<=100:
      
   print(i)
      
   i = i + 1

    • # To exit from/break a loop at any time:
while True:
      
   # ...
            
   if timer==0:
      
      break

      • 

    

  • 

    settingsFunctionsstat_minus_1
    

      

    • # Define a new proceduredef displayBanner(message):
      
   print("---------------")
      
   print(message)
      
   print("---------------")
      

      
# Procedure call
displayBanner("Hello World!")
      • 

    • # Define a new functiondef add(x, y):
      
   sum = x + y
      
   return sum
      

      
# Function call
total = add(1,3)

      print(total)  # this would display 4

      •  

    

  • 

    match_caseString Manipulationstat_minus_1
    

      

    • 
# String Concatenation
firstname = "James"
      
lastname = "Bond"
      
greeting = "Hello " + firstname + " " + lastname
       
print(greeting)
      • 

    • 
# Casting a number into a String
number = 7
      
print("Your lucky number is " + str(number))

    • 
# Changing the case of a string
name = "james BOND"
      
uppercase = name.upper() # JAMES BOND
      
lowercase = name.lower() # james bond
      
titlecase = name.title() # James Bond
      

    • 
# Retrieving the number of characters in a string
password = "Pa55w0rd"
      
passwordLength = len(password) # 8
      

    • 
# String Slicing: Extracting characters from a string	
alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
      
print("The fifth letter of the alphabet is: " + alphabet[4])
      
print("The first 5 letters of the alphabet are: " + alphabet[:5])
      
print("The next 5 letters of the alphabet are: " + alphabet[5:10])
      
print("The last 5 letters of the alphabet are: " + alphabet[-5:])

    • 
# Iterate through all the characters of a string
string = "Hello World"
      
for character in string:
      
   print(character)

    

  • 

    live_helpRandom Librarystat_minus_1
    
 
      

    • 
# Import the random library
import random
      

    •   
# Generate a random number between 1 and 100
randomNumber = random.randint(1,100)

    • 
# Pick a value in a list at random
names = ["Fred","Ali","Ines"]
      
randomName = random.choice(names)
    • 
# To shuffle a list
numbers = [1,2,3,4,5]
      
random.shuffle(numbers)
      • 

    •   
# Use ASCII codes to generate a random letter between A and Z
randomLetter = chr(random.randint(65,90))

    

  • 

    storageData Structures: Lists, Tuples and Dictionariesstat_minus_1
    

    • 
# Declaring a list and accessing its values
days = ["Mon","Tue","Wed","Thu","Fri","Sat"]
      
days.append("Sun")
      
print(days[0])      # "Mon"
      
print(days[1])      # "Tue"
      
print(days[2])      # "Wed
      
…
      
print(days[6])      # "Sun"

    • 
# Finding out the number of items in a list (length of a list)
print(len(days)) # 7

    • 
# Iterate through all the values of a list
for i in range(0,len(days)):
      
   print(days[i])

    • 
# Iterate through all the values of a list - Alternative method
for value in days:
      
   print(value)

    • 
# Adding a new value at the end of a list
numbers = [1,3,5]
      
numbers.append(7)

    • 
# Removing a value from a list
days = ["Mon","Tue","Wed","Thu","Fri"]
      
numbers.remove("Wed")

    • 
# Removing a value from a list at a given position
days = ["Mon","Tue","Wed","Thu","Fri"]
      
numbers.pop(2) # remove the third item from this list: "Wed"
      

    • 
# Declaring a tuple
magenta = (255,0,255)
      
print("R: " + str(magenta[0]))
      
print("G: " + str(magenta[1]))
      
print("B: " + str(magenta[2]))

    • 
# Using a Dictionary (Hash table)
dictionary = {"One":"Un", "Two":"Deux", "Three":"Trois"}
      
print("One in French is " + dictionary["One"])
      • 

    • 
# Adding an extra key to a dictionary
dictionary["Four"] = "Quatre" 

    

  • 

    descriptionFile Handlingstat_minus_1
    

      

    • 
# Reading a text file, line by line
file = open("myTextFile.txt","r")
      
for line in file:
      
   print(line)
      
file.close()

    • 
# Reading and extracting data from a CSV file, line by line
file = open("myTextFile.txt","r")
      
for line in file:
      
   data = line.split(",")
      
   print(data[0] + " - " + data[1] + " - " + data[2])
      
file.close()

    • 
# Overwriting the content of a text file
file = open("myTextFile.txt","w")
      
file.write("Hello World\n")
      
file.close()

    • 
# Appending data at the end of a text file
file = open("myTextFile.txt","a")
      
file.write("Hello World\n")
      
file.close()

    

  • 

    select_check_boxInput Validationstat_minus_1
    

      

    • 
# Input Validation: Presence Check
name = input("Enter your name:")
      
if name=="":
      
   print("Empty name!")
      
else:
      
   print("Thank you!")

    • 
# Input Validation: Type Check – Integer?
number = input("Type a number:")
      
if number.isdigit():
      
   print("This is a number")
      
else:
      
   print("This is not a whole number")

    • 
# Input Validation: Range Check
number = int(input("Type a number between 1 and 5:"))
      
if number>=1 and number<=5:
      
   print("Valid number")
      
else:
      
   print("Invalid number")

    • 
# Input Validation: Lookup Check
drive = input("Can you drive?").lower()
      
if drive in ["yes","no"]:
      
   print("Valid answer")
      
else:
      
   print("Invalid answer")

    • 
# Input Validation: Character Check
email = input("Type your e-mail address:")
      
if "@" in email:
      
   print("Valid e-mail address")
      
else:
      
   print("Invalid e-mail address")

    • 
# Input Validation: Length Check
password = input("Type a password:")
      
if len(password)>=8:
      
   print("Valid password")
      
else:
      
   print("Invalid password")

    • 
# Try Again! Using a While Loop:
name = input("Enter your name:")
      
while name=="":
      
   print("You must enter your name! Please try again!")
      
   name = input("Enter your name:")
      
print("Welcome " +  name)

    

  • 

    manufacturingOOPstat_minus_1
    

      

    • import random

      
# Defining a Dice class	
class Dice():
   # Constructor for the Dice class
   def __init__(self,numberOfSides=6):
      
      self.numberOfSides = numberOfSides
      
      self.value = 1

      
   def throw(self):
      
      self.value = random.randint(1,self.numberOfSides)
      
      return self.value

      
# Instantiating a dice object using the Dice class   
dice = Dice(6)
      
dice.throw()
      
print(dice.value)