【python】An Introduction to Interactive Programming in Python(week two)

This is a note for https://class.coursera.org/interactivepython-005

 

In week two, I have learned:

1.event-drvien programing

4 event types:

Input: button, textbox

Keyborad: key up, key down

Mouse: click, drag

Timer

example:

# Example of a simple event-driven program



# CodeSkulptor GUI module

import simplegui



# Event handler

def tick():

    print "tick!"



# Register handler

timer = simplegui.create_timer(1000, tick)



# Start timer

timer.start()

 

2. global variables

when you want to change the global variables, use global, ifelse you don't need global.(不需更改全局变量，只是想使用全局变量的值的时候，不需要声明global)

 

3. simpleGUI

Program structure with 7 steps:

①Globals (state)

②Helper functions

③Classes

④Define event handlers

⑤Create a frame

⑥Register event handlers

⑦Start frame & timers

# SimpleGUI program template



# Import the module

import simplegui



# Define global variables (program state)

counter = 0

# Define "helper" functions

def increment():

    global counter

    counter = counter + 1

    

# Define event handler functions

def tick():

    increment()

    print counter



def buttonpress():

    global counter

    counter = 0

    

# Create a frame

frame = simplegui.create_frame("SimpleGUI Test", 100, 100)

frame.add_button("Click me!", buttonpress)

# Register event handlers

timer = simplegui.create_timer(1000, tick)



# Start frame and timers

frame.start()

timer.start()

 

Simple Calculator

Data 

　　Store

　　Operand

Operations

　　print

　　Swap

　　Add

　　Subtract

　　Multiple

　　Divide

Computation

　　Store = store operation operand

# calculator with all buttons





import simplegui



# intialize globals

store = 0

operand = 0





# event handlers for calculator with a store and operand



def output():

    """prints contents of store and operand"""

    print "Store = ", store

    print "Operand = ", operand

    print ""

    

def swap():

    """ swap contents of store and operand"""

    global store, operand

    store, operand = operand, store

    output()

    

def add():

    """ add operand to store"""

    global store

    store = store + operand

    output()



def sub():

    """ subtract operand from store"""

    global store

    store = store - operand

    output()



def mult():

    """ multiply store by operand"""

    global store

    store = store * operand

    output()



def div():

    """ divide store by operand"""

    global store

    store = store / operand

    output()



def enter(t):

    """ enter a new operand"""

    global operand

    operand = int(t)

    output()

    

# create frame

f = simplegui.create_frame("Calculator",300,300)



# register event handlers and create control elements

f.add_button("Print", output, 100)

f.add_button("Swap", swap, 100)

f.add_button("Add", add, 100)

f.add_button("Sub", sub, 100)

f.add_button("Mult", mult, 100)

f.add_button("Div", div, 100)

f.add_input("Enter", enter, 100)





# get frame rolling

f.start()