python pass是空语句，是为了保持程序结构的完整性。
python 语言 pass 语句语法格式如下：
pass
实例：
#!/usr/bin/python
for letter in ‘python’:
if letter == ‘h’:
pass
print ‘this is pass block’
print ‘current letter :’, letter
print “good bye!”
以上实例执行结果：
current letter : p
current letter : y
current letter : t
this is pass block
current letter : h
current letter : o
current letter : n
good bye!