【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()
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