《Python基础教程》第二版代码清单2-3更正

# 以正确的宽度在一个居中的“盒子”内打印一个句子
sentence = raw_input('Sentence: ')
screen_width = 80
text_width = len(sentence)
box_width = text_width + 24
left_margin = (screen_width - box_width) // 2
print
print ' ' * left_margin + '+' + '-' * (box_width-2) + '+' 
print ' ' * ((screen_width- text_width - 4) // 2) + '| ' + ' ' * text_width + ' |'
print ' ' * ((screen_width- text_width - 4) // 2) + '| ' + sentence + ' |'
print ' ' * ((screen_width- text_width - 4) // 2) + '| ' + ' ' * text_width + ' |'
print ' ' * left_margin + '+' + '-' * (box_width-2) + '+'
print