在if语句中传递语句

Question

我试着理解,在这段代码中,为什么python打印这封信"w"？(我使用python 2.7.8):

LetterNum = 1

for Letter in 'Howdy!':
    if Letter == 'w':
        pass
        print 'Encountered w, not processed.'
    print ('Letter', LetterNum, 'is', Letter)
    LetterNum+= 1

我得到这个结果:

>>> 
('Letter', 1, 'is', 'H')
('Letter', 2, 'is', 'o')
Encountered w, not processed.
('Letter', 3, 'is', 'w')
('Letter', 4, 'is', 'd')
('Letter', 5, 'is', 'y')
('Letter', 6, 'is', '!')

虽然我认为我应该得到这个结果:

>>> 
('Letter', 1, 'is', 'H')
('Letter', 2, 'is', 'o')
Encountered w, not processed.
('Letter', 4, 'is', 'd')
('Letter', 5, 'is', 'y')
('Letter', 6, 'is', '!')
>>>  

Answer 1

您正在尝试使用pass,就像它继续一样.传递不执行任何操作,而继续跳过当前迭代.以下代码可以正确使用continue来执行您想要的操作:

LetterNum = 1

for Letter in 'Howdy!':
    if Letter == 'w':
        print 'Encountered w, not processed.'
        continue
    print ('Letter', LetterNum, 'is', Letter)
    LetterNum+= 1