判断字典是否存在某个key
s = {'a':'1', 'b':'2', 'c':'3'}
print s.has_key('d')
False
print s.has_key('a')
True
print 'a' in s
True
print 'd' in s
False
s = {'a':'1', 'b':'2', 'c':'3'}
print s.has_key('d')
False
print s.has_key('a')
True
print 'a' in s
True
print 'd' in s
False