Python Unit

Transcription

1 Python Unit : Advanced print() and input() commands 2.2: Functions and Variable Scope 2.3: Flowcharting The Dragon Realm text-based game

2 Python 2.1 Advanced print() and input() commands

3 Objectives By the end of this unit, you will be able to: Use the end keyword for the print() command to skip newlines. Utilize escape characters Combine the print() and input() commands

4 Print() and the end Keyword The end= is a special command that tells Python not to place a carriage return at the end of the text printed by the print() statement. print('interrupting cow wh', end='') print('-moo!') Result: Interrupting cow wh -MOO!

5 Programming Issue We want to print: What do dentists call an astronaut's cavity? Will this syntax work? print('what do dentists call an astronaut's cavity?') One of the best solutions to this issue are escape characters?

6 Escape Characters print('what do dentists call an astronaut\'s cavity?') input() print('a black hole!') The slash is an escape character that says print the apostrophe ( ). Don t count it as a way to identify a string. There are other things we may want Python to ignore as syntax.

7 Escape Characters Escape Character What Prints \\ Backslash (\) \' Single quote (') \" Double quote (") \n Newline \t Tab

8 Reading / Exercise(s) Read Chapter 5 Jokes in the Invent Your Own Games textbook. Complete the exercises found on Intranet under Game Development/Exercises: Link goes here

9 Python 2.2 Functions and Variable Scope

10 Objectives By the end of this unit you will be able to: Create functions to reuse code and improve the structure of your program. Use the return keyword to pass a value out of a function Use the and, not, and or operators in expressions Understand and utilize variable scope Understand and utilize parameters

11 Function Like a mini-program Helps you avoid writing the same code multiple times in your module. This is essential to programming. Uses def to define the function Only executes when called

12 Functions We Have Already Seen print() input() int() random.randint()

13 Function Syntax

14 Example Function # This function prints the string Hello World def helloworld(): print('hello World') # Here is where we call the function. helloworld() Note: Functions must be defined above where they are executed.

15 The Dragon Realm Program The dragon Realm Program: 1. Allows the player to select cave one or two. 2. Determines if an evil or generous dragon resides in the cave. 3. Punishes or rewards the player depending on the result.

16 Dragon Realm Functions displayintro() Sets up the game by displaying information about the caves, loot and dragon. choosecave() Asks the player to select cave 1 or 2 Returns the players choice to the main program. checkcave() The player s selected cave # is passed into the function. Generates a random number to determine which cave is friendly. Tells the player whether they received treasure or were eaten.

17 The choosecave() Function (return statement) def choosecave(): cave = '' while cave!= '1' and cave!= '2': print('which cave will you go into? (1 or 2)') cave = input() return cave

18 Calling the choosecave() Function # Call the choosecave() function cavenumber = choosecave() Value returned from choosecave() is placed in the cavenumber variable. The cavenumber string can be used later in the module.

19 The checkcave() Function def checkcave(chosencave):... a bunch of print and sleep statements go here friendlycave = random.randint(1, 2) if chosencave == str(friendlycave): print('gives you his treasure!') else: print('gobbles you down in one bite!') chosencave is a parameter passed into the function.

20 Function Parameters # name this function s parameter. def sayhello(name): print('hello, ' + name) # First execution passing string sayhello( Teacher ) What is the result??? What about: sayhello( Dingleberry )

21 Variable Scope Scope Defines where a variable can be referenced or modified. o Defined by where it was created: Global Scope - Global variables are created outside of functions. o Available outside and inside of all functions in module. o Can be read, but not modified within a function. Local Scope Local variables are created inside functions. o Can only be read or modified inside of the function. WARNING: Be careful to give your local and global variables different names.

22 Variable Scope Example myglobalname = 'Pete Global' def sayhello(): mylocalname = 'Pete Local' print('hello, ' + mylocalname) print('hello, ' + myglobalname) sayhello() What is the result of this function?

23 Variable Scope Warning If you try to modify the global variable within a function, an UnboundLocalError message results.

24 Where does the Dragon Realm Program Start Executing? After all functions and classes are defined oclasses are awesome and discussed later in this class. Look at the program together

25 Reading / Exercises Read Chapter 6 Dragon Realm in the Invent Your Own Games textbook. Complete the exercises found on Intranet under Game Development/Exercises: Link goes here

26 Python 2.3 Flowcharting

27 Objectives By the end of this unit you will be able to: Design programs using flowcharting

28 The Author s Weak Dragon Realm Flowchart

29 Program Design Flowchart A technique to design programs using symbols. Why Flowchart: Documentation Helps plan and organize your program Keeps you from missing stuff Improves development speed

30 Common Flowcharting Symbols Terminal Indicates the beginning or end of a program. Oval Shaped

31 Common Flowcharting Symbols The program does something Typically functions or methods.

32 Common Flowcharting Symbols Indicate data going in or out of your program. At this point, think input() or print() functions. Slanted rectangle shape

33 Common Flowcharting Symbols Decision logic within the program Used for if statements, loops, etc. Diamond Shaped

34 Common Flowcharting Symbols Things reported to user Use when: Non-basic information is displayed for user For printed reports. Curvy rectangle shaped

35 Common Flowcharting Symbols Allows jumping to other parts of flowchart. Helps avoid overlapping lines.

36 New Dragon Realm Flowchart

37 Gliffy.com 1. Surf to 2. Login with my gmail account: 3. Draw a simple flowchart containing terminals, processes and decisions.

38 Gliffy Interface

39 Reading / Exercises Complete the exercises found on Intranet under Game Development/Exercises:

40 Unit Exam