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Copy pathtypewriter.py
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109 lines (79 loc) · 2.24 KB
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"""This module contains a code example related to
Think Python, 2nd Edition
by Allen Downey
http://thinkpython2.com
Copyright 2015 Allen Downey
License: http://creativecommons.org/licenses/by/4.0/
"""
from __future__ import print_function, division
import string
import turtle
"""
To use this typewriter, you have to provide a module named letters.py
that contains functions with names like draw_a, draw_b, etc.
"""
# check if the reader has provided letters.py
try:
import letters
except ImportError as e:
message = e.args[0]
if message.startswith('No module'):
raise ImportError(message +
'\nYou have to provide a module named letters.py')
def teleport(t, x, y):
"""Moves the turtle without drawing a line.
Postcondition: pen is down
t: Turtle
x: coordinate
y: coordinate
"""
t.pu()
t.goto(x, y)
t.pd()
def keypress(char):
"""Handles the event when a user presses a key.
Checks if there is a function with the right name; otherwise
it prints an error message.
char: string, letter to draw
"""
# if we're still drawing the previous letter, bail out
if bob.busy:
return
else:
bob.busy = True
# figure out which function to call, and call it
try:
name = 'draw_' + char
func = getattr(letters, name)
except AttributeError:
print("I don't know how to draw an", char)
bob.busy = False
return
func(bob, size)
letters.skip(bob, size/2)
bob.busy = False
def carriage_return():
"""Moves to the beginning of the next line.
"""
teleport(bob, -180, bob.ycor() - size*3)
bob.busy = False
def presser(char):
"""Returns a function object that executes keypress.
char: character to draw when the function is executed
returns: function with no arguments
"""
def func():
keypress(char)
return func
# create and position the turtle
size = 20
bob = turtle.Turtle()
bob.busy = False
teleport(bob, -180, 150)
# tell world to call keypress when the user presses a key
screen = bob.getscreen()
for char in string.ascii_lowercase:
screen.onkey(presser(char), char)
screen.onkey(carriage_return, 'Return')
screen.listen()
turtle.mainloop()