Python Touch is designed for students to write python code on a tablet computer

Features:

• Write python code with syntax highlighting (pretty colours to help prevent errors)
• Run python code on any device
• Debug python line by stepping through line-by-line
• View contents of variables as you step through a program
• Browse and try out sample python code
• Save and load python programs hidden inside images on your camera roll

Samples

• Quick Start

  • Hello World

    # use print to display messages
    
    print("Hello world")
    

  • Draw

    # import turtle drawing module
    import turtle 
    
    print "Click on Drawing Canvas to see turtle graphics"
    
    draw = turtle.Turtle()
    draw.penup()
    
    # draw text
    draw.color("#3978AE")
    draw.goto(0,20)
    draw.write("Python")
    
    draw.color("#FFD344")
    draw.goto(0,0)
    draw.write("Touch")
    
    # draw shape
    draw.goto(-30, -20)
    draw.pendown()
    draw.color("black")
    for i in range(2):
        draw.forward(100)
        draw.left(90)
        draw.forward(70)
        draw.left(90)
        
    
    

  • Chat bot

    # Template for a chatbot - a simple program that asks you questions and responds
    
    print("Hello! My name is chatbot")
    
    name = input("What's your name?")
    print("Hi " + name)
    
    age = int(input("How old are you?"))
    if age > 100:
    	print("Really? That's pretty old!")
    else:
        difference = 100 - age
        print("You'll be 100 in " + str(difference) + " years")
        
    # add your own questions here 
    
    

• AQA GCSE Computer Science from 2016

  These samples are designed to cover the AQA GCSE Computer Science (from 2016)

  These resources are not affiliated to or endorsed by AQA in any way.

  • Data Types

    • Integer

      print """
      integers are whole numbers (not fractions or decimals)
      """
      
      print("These are integers (whole numbers)")
      
      print(1)
      print(10)
      print(33)
      
      

    • Real

      print """
      Real numbers can contain decimal places (e.g. 3.141)
      Python calls reals floats or floating point numbers
      """
      
      print("These are reals (floating point or decimal numbers)")
      print(1.45)
      print(3.1412)
      print(1.0)
      

    • Boolean

      print """
      Boolean means either True or False - nothing else.
      """
      
      print("These are booleans")
      print(True)
      print(False)
      

    • Character

      print """
      A character is one letter or symbol
      In python there's no difference between the data type that stores one character or lots of characters: they're both stored in strings.
      """
      
      print("These are characters (single letters or digits)")
      
      # Note that you can use either single quotes ' or double quotes " as long as you use the same one either side of the character.
      print("A")
      print("1")
      print("*")
      print('"')
      

    • String

      print """
      A string is one or more letter or symbol
      In python there's no difference between the data type that stores one character or lots of characters: they're both stored in strings.
      """
      
      print("These are strings (one or more characters)")
      print("Hello")
      print("Howdi")
      
      # notice that this next one is still a string even though it looks like a number. It's a string because it's surrounded by quotation marks.
      print("12345")
      

  • Programming Concepts

    • Variable declaration

    print """ 
    Variables store data that might change while the program runs.
    Variables in python should be given a suitable name that describes the data stored inside. 
    Choosing variable names carefully (rather than variable1 or thingy) makes your code easier to understand. 
    You should follow the PEP8 convention for choosing variable names: lowercase_words_separated_by_underscores
    """
    
    # integer variable
    age = 8
    
    # real variable
    top_speed = 4.32
    
    # boolean variable
    hungry = True
    
    # character variable
    key_to_quit = "Q"
    
    # string variable
    user_name = "Bob"
    
    # display the variables
    print "Integer variable:", age
    print "Real variable:", top_speed
    print "Boolean variable:", hungry
    print "Character variable:", key_to_quit
    print "String variable:", user_name
    
                    

    • Constant declaration

    print """ 
    Constants store data that you set in your code and never change while the program runs.
    Constants in python should be given a suitable name that describes the data stored inside. 
    Choosing constant names carefully (rather than variable1 or thingy) makes your code easier to understand. 
    You should follow the PEP8 convention for choosing constant names: UPPERCASE_SEPARATED_BY_UNDERSCORES
    """
    # integer constant
    AGE = 8
    
    # real constant
    TOP_SPEED = 4.32
    
    # boolean constant
    HUNGRY = True
    
    # character constant
    KEY_TO_QUIT = "Q"
    
    # string constant
    USER_NAME = "Bob"
    
    # display the constants
    print "Integer constant:", AGE
    print "Real constant:", TOP_SPEED
    print "Boolean constant:", HUNGRY
    print "Character constant:", KEY_TO_QUIT
    print "String constant:", USER_NAME
                    

    • Assignment

    print """
    Assignment means setting the value of a variable.
    This means that the variable stores that value so it can be used or changed later.
    """
    
    # Assign (store) the real number 3.141 into a constant called PI
    PI = 3.141
    
    # assign the integer number 10 to a variable called radius
    radius = 10
    
    # calculate the area (pi times radius squared) and assign it to a variable called area
    area = PI * radius * radius
    
    print area
    
    
                    

    • Definite iteration

    print """
    Iteration means looping through each of multiple values
    Definite iteration means you know in advance exactly how many times the loop will repeat.
    """
    
    # Display each letter of the alphabet
    for letter in "abcdefghijklmnopqrstuvwxyz":
    	print letter
        
    # Display each number between 1 and 10
    for i in [1,2,3,4,5,6,7,8,9,10]:
    	print i
        
    # Display each number between 1 and 100
    for i in range(100):
    	print i
                    

    • Indefinite iteration

    print """
    Iteration means looping (repeating) multiple times
    Indefinite iteration means you don't know in advance exactly how many times the loop will repeat
    """
    
    # keep looping until the user types "exit"
    while raw_input("Type exit to quit") != "exit":
    	print("OK, I'll keep looping")
                    

    • Nested iteration

    # iteration means repeating some code multiple times.
    # Nested iteration means having a loop within a loop
    
    # make a list containing each day of the week
    days = ["Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun"]
    
    # outer loop: iterate through days of the week
    for day in days:
    	
        # inner loop: iterate through each of the hours in a day
        for hour in range(24):
        
        	print day, hour, ": 00"
    

    • Selection

    print """
    Selection happens when your program makes a choice between doing one thing or another.
    In python, "if" lets you run code based on the answer to a question / condition.
    """
    
    # choose a random number 
    import random
    random_number = str(random.randint(1,10))
    
    # let the user guess
    guess = raw_input("I've chosen a random number between 1 and 10. Guess what it is")
    
    # does the user's guess match the random number?
    if random_number == guess:
    	print "Correct!"
    else:
    	print "Wrong: I guessed " + random_number
                    

    • Nexted selection

    print """
    Selection means making your code only run if a condition is met.
    Nested selection means an if statement inside an if statement - checking to see if two conditions are met.
    """
    
    str_number = raw_input("Please enter a number over 100")
    if str_number.isdigit():
        int_number = int(str_number) 
        
        # nested selection: "if" inside an "if"
        if int_number > 100:
        	print "Thank you"
        else:
        	print "The number must be over 100"
    else:
    	print "You must type in a number"
                    

    • Subroutine

    print """
    A subroutine is a section of code that you can re-use more than once. This makes your code more efficient as you end up writing less code.
    You have to give each subroutine a name. This can help your code be more readable.
    """
    
    # import the turtle module to draw shapes
    import turtle
    t = turtle.Turtle()
    
    # define a procedure (subroutine) called draw_square
    def draw_square(x, y, size):
        
        # move to x, y
        t.penup()
        t.goto(x,y)
        t.pendown()
        
        # draw the square
        for i in range(4):
            t.forward(size)
            t.right(90)
            
    # call the subroutine to draw a square at (0,0)
    draw_square(0, 0, 10)
    
    # call the subroute again, drawing a square at (100,100)
    draw_square(100,100, 30)
    

    • Choosing identifier names

    print """
    An identifier name is the name of a variable, constant, function or procedure.
    In order to make your code consistent and easy to understand / maintain, you should name your variables / constants in a way that describes the data that they store
    Similarly, you should name procedures or functions in a way that describes what those subroutines do.
    
    For further info, read the Python Style Guide (PEP8): https://www.python.org/dev/peps/pep-0008/
    """
    
    # bad examples:
    variable1 = "Hello"
    n = "Bob"
    number = 27
    
    # better examples, but not in line with PEP8
    EnglishGreeting = "Hello"
    Name = "Bob"
    ageOfPerson = 27
    
    # advised way of doing things according to PEP8
    english_greeting = "Hello"
    name = "Bob"
    age_of_person = 27
    

  • Operators

    • Arithmetic operators

      print """
      An operator lets perform an action (or operation) on some data
      An arithmetic operator means performing an addition / subtraction / multiplication or division on some numbers
      """
      
      # addition
      print "+ is the addition operator"
      answer = 10 + 100
      print "10 plus 100 = ", answer
      
      # subtraction
      print "- is the subtraction operator"
      answer = 100 - 10
      print "100 minus 10 = ", answer
      
      # multiplication
      print "* is the multiplication operator"
      answer = 10 * 10
      print "10 times 10 = ", answer
      
      # real division
      print "/ is the division operator"
      answer = 50.0 / 7.0
      print "50 divided by 7 = ", answer
      
      # integer division
      print "% is the modulo operator (used to find the remainder after an integer division)"
      answer = 50 / 7
      remainder = 50 % 7
      print "50 divided by 7 is", answer, "with a remainder of", remainder
      

    • Relational operators

      print """
      An operator lets perform an action (or operation) on some data
      A relational operator means comparing two pieces of data 
      
      This sample asks the user to type in a number and then compares that number to the number 10
      """
      
      # ask the user to type in a number
      user_number = int(raw_input("Please enter a number"))
      
      # equal to
      if user_number == 10:
          print "Your number is equal to 10"
      
      # not equal to
      if user_number != 10:
          print "Your number is not equal to 10"
          
      # less than
      if user_number < 10:
          print "Your number is less than 10"
          
      # greater than
      if user_number > 10:
          print "Your number is greater than 10"
      
      # less than or equal to
      if user_number <= 10:
          print "Your number is less than or equal to 10"
          
      # greater than or equal to
      if user_number >= 10:
          print "Your number is greater than or equal to 10"
      

    • Boolean operators

      print """
      An operator lets perform an action (or operation) on some data
      Boolean data is either something that is True or False.
      A boolean operator can combine or change boolean data (and / or / not)
      
      This sample asks the user if they are hungry and/or thirsty then analyses the answers
      """
      
      # ask the user if they're hungry
      hungry = raw_input("Please type yes if you're hungry")
      
      # check if they type in "yes"
      bool_hungry = hungry == "yes"
      
      # Check if the user is thirsty
      bool_thirsty = raw_input("Please type yes if you're thirsty") == "yes"
      
      # show results
      print "Hungry:", bool_hungry
      print "Thirsty", bool_thirsty
      
      # NOT
      print "NOT hungry:", not bool_hungry
      print "NOT thirsty:" , not bool_thirsty
      
      # AND
      print "Hungry AND thirsty:", bool_hungry and bool_thirsty
      
      # OR
      print "Hungry OR thirsty:", bool_hungry or bool_thirsty
      
      

  • Data structures

    • Arrays (lists)

      print """
      A list in python is an array: it can stores  more than one pieces of data in order.
      
      A one dimensional array is a single list.
      A two dimensional array is a list of different lists
      """
      
      # list of animals
      animals = ["dog", "cat", "donkey", "chicken"]
      
      # loop through each item in list
      for animal in animals:
          print "Old McDonald had a farm, E-i-e-i-oh"
          print "And on that farm he had a", animal, "e-i-e-i-oh"
          
      # You can think of strings as an array of characters.
      # e.g. "dog" is pretty much the same as ["d", "o", "g"]
      
      
      print "The first letter of the first animal is:", animals[0][0]
      
      print "The first letter of the last animal is", animals[-1][0]
      
      print "The 2nd letter of the 3rd animal is", animals[1][2]
      

    • Records (dictionaries)

      print """
      A dictionary in python is a record: it can structure data in a way so that linked data is stored together
      
      A dictionary works with pairs of keys and values: you look up a key to find a value.
      This works the same way as an old fashioned paper dictionary: you look up a word (key) to find its meaning (value)
      """
      
      # create a dictionary for each animal
      dog = {"name": "dog", "noise": "woof"}
      cat = {"name": "cat", "noise": "miaow"}
      donkey = {"name": "donkey", "noise": "eee-or"}
      chicken = {"name": "chicken", "noise": "cluck"}
      
      # list of animals
      animals = [dog, cat, donkey, chicken]
      
      # loop through each dictionary in list
      for animal in animals:
          print "Old McDonald had a farm, E-i-e-i-oh"
          print "And on that farm he had a", animal["name"], "e-i-e-i-oh"
          print "With a", animal["noise"], animal["noise"], "here and a", animal["noise"], animal["noise"], "there"
          print "Here a", animal["noise"], "there a", animal["noise"], "everywhere a", animal["noise"], animal["noise"]
          print "Old McDonald had a farm, E-i-e-i-oh"
          print
          
      
      

  • Input / Output

    • User input from keyboard

      print """
      Most programs need to ask the user questions and let them type in their answers.
      
      This sample asks the user what their name is and responds by saying hello
      """
      
      # ask question and save answer into variable called name
      name = raw_input("What is your name?")
      
      # display greeting
      print "Hello", name
      
      

    • Output to screen

      print """
      Most programs need to display text or data to the screen.
      
      This sample shows how to display text and the contents of a variable
      """
      
      # create a variable called hello and save the string "Bonjour" to it
      hello = "Bonjour"
      
      # display the string "hello"
      print "hello"
      
      # display the contents of the variable called hello
      print hello
      
      

    • Reading from and writing to text files

      print """
      The data stored in variables is lost when a program stops running. 
      Saving data to a file allows your program to store is so that it can read next time it runs. 
      
      This sample asks the user a question and shows what they typed in last time they ran the program
      """
      
      try:
      	# open data.txt in read mode
      	input_file = open("data.txt", "r")
      	previous_answer = input_file.read()
      	input_file.close()
      	
      except:
      	previous_answer = "Could not open data.txt. Perhaps this is the first time you've run this program?"
      
      # ask for highligh of the day
      this_answer = raw_input("What's been the highlight of your day today?")
      
      # save answer
      output_file = open("data.txt", "w")
      output_file.write(this_answer)
      output_file.close()
      
      print "Thank you. Your answer has been saved. Last time you ran the program you said the highlight of your day was:"
      print previous_answer
      
      

    • Exporting data to a CSV file

      print """
      Python can write data to CSV files which can be easily imported into a spreadsheet (e.g. Excel)
      
      This sample exports a file called fruit.csv with the colours of different fruit.
      """
      # Store data in a 2D list (a list of lists)
      data = [["Fruit", "Colour"],
              ["Tomato", "Red"],
              ["Lemon", "Yellow"]]
              
      # import comma separated values module
      import csv
      
      # open file in binary write mode
      file_object = open("fruit.csv", "wb")
      
      # create csv writer object
      writer = csv.writer(file_object)
      
      # write data to file
      writer.writerows(data)
      
      # close file
      file_object.close()
      

    • Importing data from a CSV file

      print """
      Python can read data from CSV files which can be easily exported from a spreadsheet (e.g. Excel)
      
      This sample loads data from a file called fruits.csv (Check samples to create a sample of this file).
      """
      
      # import comma separated values module
      import csv
      
      # open file in binary read mode
      file_object = open("fruit.csv", "rb")
      
      # create csv reader object
      reader = csv.reader(file_object)
      
      # loop through each line in the file
      for row in reader:
          print row
      
      # close file
      file_object.close()
      

  • String handling

    • String length

      print """
      A string is one or more characters (letters or symbols) in order, usually in a way that spells out a word or sentence, but it can store any text.
      
      The length of a string is the number of characters. E.g. the length of "hello" is 5 because there are 5 characters
      
      This sample asks the user to type in a string. It then counts how many characters are in that string.
      """
      
      # ask user to type in a string
      user_string = raw_input("Type in anything here:")
      
      # calculate the length
      length = len(user_string)
      
      # display the result
      print "The length of the string you typed in is:", length
      
      

    • String position

      print """
      A string is one or more characters (letters or symbols) in order, usually in a way that spells out a word or sentence, but it can store any text.
      
      This sample asks the user to type in a string containing the letter "a". 
      It then displays where the letter "a" is first found in the string that the user entered.
      """
      
      # ask user to type in a string
      user_string = raw_input("Type in anything here that contains the letter 'a':")
      
      # calculate the first position of 'a'
      position = user_string.index('a')
      
      # display the result
      print "The letter a first appears as character in position", position
      

    • Substring

      print """
      A string is one or more characters (letters or symbols) in order, usually in a way that spells out a word or sentence, but it can store any text.
      
      A substring is some of the characters that makes up part of a string. E.g. "hell" is a substring of "hello"
      
      This sample asks the user to choose the first and last characters of a nursery rhyme.
      It then displays the substring between the first and last characters that they choose
      """
      
      rhyme = """Jack and Jill went up the hill
      To fetch a pail of water.
      Jack fell down and broke his crown,
      And Jill came tumbling after"""
      
      length = len(rhyme)
      
      print "Here's a nursery rhyme that is", length, "characters long:"
      print rhyme
      
      start = int(raw_input("Choose substring start number:"))
      end = int(raw_input("Choose substring end number:"))
      
      print "Here's your substring:", rhyme[start:end]
      

    • String concatenation

      print """
      A string is one or more characters (letters or symbols) in order, usually in a way that spells out a word or sentence, but it can store any text.
      
      Concatenation means joining together. E.g. concatenating the strings "im" and "possible" makes the string "impossible"
      
      This sample chooses 10 random letters and joins them together to make a secure password
      """
      
      # make a string with all the possible characters in
      characters = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXVZ1234567890!$%^&*()"
      
      # import the random module
      import random
      
      # start with an empty password
      password = ""
      
      # loop 10 times, using the variable i to count from 0 to 9
      for i in range(10):
      	# concatenate (add on) a random character on to the end of the password
      	password = password + random.choice(characters)
      
      print "A random 10 digit password for you to us is:", password
      	
      

    • Character conversion

      print """
      Characters are single letters, digits or symbols.
      Each character in the US alphabet is stored as an ASCII number. 
      E.g. The character "A" is the decimal ASCII number 65 and "a" is the decimal ASCII number 97
      
      You can use ord() and chr() to convert between characters and ASCII numbers
      
      This sample lets the user convert to and from characters / ascii numbers
      """
      
      number = int(raw_input("Please enter a number between 0 and 127 to convert to a character:"))
      character = chr(number)
      print "The ASCII number", number, "represents the character", character
      
      character = raw_input("Please enter a single character:")
      number = ord(character)
      print "This character", character, "is represented by the ASCII number", number
      
      

    • String conversions

      print """
      A string is data made up of one or more characters e.g. "hello"
      
      This sample converts strings to integers / real (float)  data types and vice versa.
      """
      
      string_number = "100"
      print "When you multiply the string '100' by two you get", string_number * 2
      
      # convert from string to int
      int_number = int(string_number)
      print "When you multiply the integer 100 by two you get", int_number * 2
      
      # convert from string to real
      float_number = float(string_number)
      print "When you multiply the float / real number 100.00 by 2.00 you get", float_number * 2.0
      
      print "You can convert any data type to a string using the str() function"
      
      # convert to string
      print "Here are some examples: ", str(2.0), str(1), str(True)
      
      

  • Choosing at random

    • Random numbers

      print """
      Getting a completely logical machine such as a computer to choose a random number is a surprisingly complex task.
      Thankfully, Python has a random module that makes it really easy.
      
      This sample shows how to choose a random number between a minimum and maximum value
      """
      
      # load random module
      import random
      
      print "Random number between 1 and 10:"
      print random.randint(1,10)
      
      print "Random number between 0.5 and 0.75:"
      print random.uniform(0.5, 0.75)
      
      

  • Sub routines (procedures and functions)

    • Procedures

      print """
      A procedure is a section of code that has been given a name that you can re-use.
      They can make your code easier to read (because you give sections of code a descriptive name)
      They can make your code more efficient (because you can re-use sections of code)
      
      This sample uses a procedure that displays a random insult to the user.
      """
      
      # load random module
      import random
      
      # define the insult procedure
      def show_insult():
      	# make lists used to generate random insult
      	adjectives = ['fat', 'funny', 'silly', 'wobbly', 'smelly', 'stinky', 'big', 'small']
      	nouns = ['face', 'nose', 'ears', 'arms', 'belly', 'toes', 'hair', 'breath']
      	
      	# display insult
      	print random.choice(adjectives), random.choice(nouns)
      
      	
      # show insult
      print "Here's a random insult:"
      show_insult()
      print "Here's another"
      show_insult()
      
      # show 10 more
      print "Here's 10 more:"
      for i in range(10):
      	show_insult()
      

    • Procedures with parameters

      print """
      A procedure is a section of code that has been given a name that you can re-use.
      A parameter is a variable that you give to the procedure that determines what it does or how it works.
      
      Parameters let you customise procedures so that they can be used for more than one purpose.
      
      This sample uses a procedure that displays a set number of random insults to the user.
      """
      
      # load random module
      import random
      
      # define the insult procedure
      def show_insult(how_many_times):
      	# make lists used to generate random insult
      	adjectives = ['fat', 'funny', 'silly', 'wobbly', 'smelly', 'stinky', 'big', 'small']
      	nouns = ['face', 'nose', 'ears', 'arms', 'belly', 'toes', 'hair', 'breath']
      	
      	# display insult
      	print "Here are your", how_many_times, "insults:"
      	
      	for i in range(how_many_times):
      		print random.choice(adjectives), random.choice(nouns)
      
      	
      # show 3 insults
      show_insult(3)
      
      # show 10 insults
      show_insult(10)
      

    • Functions that return a value

      print """
      A procedure is a section of code that has been given a name that you can re-use.
      A function is like a procedure but it returns a value that you can then use later in your program.
      
      Functions can take parameters just like procedures
      
      This sample uses a function to let the user choose one of a set number of options
      """
      
      # define a function that lets the user choose from a list of options
      def choose_from(prompt, options):
      	
      	# keep looping until the user chooses a valid option
      	while True:
      		
      		# use a dictionary to keep track of which number each of the options are
      		number_options = {}
      		
      		# display the prompt message
      		print prompt
      		
      		# loop through and display each option with its own number
      		count = 1
      		for option in options:
      			print count, ":", option
      			
      			# add to dictionary: pair up the number with the option
      			number_options[str(count)] = option
      			
      			# increase count by one
      			count += 1
      		
      		# ask user to choose an option
      		user_choice = raw_input("Which option?")
      		
      		# check if they typed in an option longhand
      		if user_choice in options:
                  
                  # return what the user 
      			return user_choice
      			
      		# check if they typed in a number
      		if user_choice in number_options:
      		    
      		    # return the option the user chose with their number
      			return number_options[user_choice]
      		
      		
      # ask the user to choose between potatoes and carrots. Save the return value into veg		
      veg = choose_from("What's your favourite vegetable?", ("Potatoes", "Carrots"))
      
      # ask the user to choose between oranges, apples and pineapples. Save the return value into fruit
      fruit = choose_from("What's your favourite fruit?", ("Orange", "Apple", "Pineapple"))
      
      
      # display their choices
      print "You chose", fruit, "and", veg	
      

Credits

# import turtle drawing module
import turtle 

print "Click on Drawing Canvas to see turtle graphics"

draw = turtle.Turtle()
draw.penup()

# draw text
draw.color("#3978AE")
draw.goto(0,20)
draw.write("Python")

draw.color("#FFD344")
draw.goto(0,0)
draw.write("Touch")

# draw shape
draw.goto(-30, -20)
draw.pendown()
draw.color("black")
for i in range(2):
    draw.forward(100)
    draw.left(90)
    draw.forward(70)
    draw.left(90)