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115 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
# here is a mostly-straightforward solution to the
# two-by-two version of the grid.
def do_twice(f):
f()
f()
def do_four(f):
do_twice(f)
do_twice(f)
def print_beam():
print('+ - - - -', end=' ')
def print_post():
print('| ', end=' ')
def print_beams():
do_twice(print_beam)
print('+')
def print_posts():
do_twice(print_post)
print('|')
def print_row():
print_beams()
do_four(print_posts)
def print_grid():
do_twice(print_row)
print_beams()
print_grid()
# here is a less-straightforward solution to the
# four-by-four grid
def one_four_one(f, g, h):
f()
do_four(g)
h()
def print_plus():
print('+', end=' ')
def print_dash():
print('-', end=' ')
def print_bar():
print('|', end=' ')
def print_space():
print(' ', end=' ')
def print_end():
print()
def nothing():
"do nothing"
def print1beam():
one_four_one(nothing, print_dash, print_plus)
def print1post():
one_four_one(nothing, print_space, print_bar)
def print4beams():
one_four_one(print_plus, print1beam, print_end)
def print4posts():
one_four_one(print_bar, print1post, print_end)
def print_row():
one_four_one(nothing, print4posts, print4beams)
def print_grid():
one_four_one(print4beams, print_row, nothing)
print_grid()
comment = """
After writing a draft of the 4x4 grid, I noticed that many of the
functions had the same structure: they would do something, do
something else four times, and then do something else once.
So I wrote one_four_one, which takes three functions as arguments; it
calls the first one once, then uses do_four to call the second one
four times, then calls the third.
Then I rewrote print1beam, print1post, print4beams, print4posts,
print_row and print_grid using one_four_one.
Programming is an exploratory process. Writing a draft of a program
often gives you insight into the problem, which might lead you to
rewrite the code to reflect the structure of the solution.
--- Allen
"""
print(comment)