Python 学习笔记 14.技巧(Tips)

转载自：http://www.xwy2.com/article.asp?id=125

多变量赋值

>>>>>> a = b = c = 1  
>>>>>> print a, b, c  
1 1 1  
>>>>>> (a, b, c) = range(3)  
>>>>>> print a, b, c  
0 1 2  
>>>>>> (a, b, c) = ("a", "b", "c")  
>>>>>> print a, b, c  
a b c  

连接字符串

>>>>>> (a, b, c) = ("a", "b", "c")  
>>>>>> print a, b, c  
a b c  
>>>>>> s = ("a", "b", "c")  
>>>>>> ",".join(s)  
'a,b,c'  
>>>>>> s = {1:"a", 2:"b", 3:"c"}  
>>>>>> ",".join(["%d:%s" % (k, v) for k, v in s.items()])  
'1:a,2:b,3:c' 

使用 0 < i < 10 要比 使用 i > 0 and i < 10 性能更好一些

>>>>>> def test(i):  
  if (0 < i < 10):  
    print "ok"  
  else:  
    print ""  
      
>>>>>> test(4)  
ok  
>>>>>> test(12)  
  
>>>>>> test(0)  
  

不要使用 ++i 来递增

Python 虽然支持 ++i，但实际表示的意思是 +(+i)，我们可以使用 i += 1 来实现递增。

>>>>>> i = -10  
>>>>>> ++i  
-10  
>>>>>> i += 1  
>>>>>> i  
-9