Unpacking operations for Python sequences and maps-Python Tutorial-php.cn

Unpacking operations for Python sequences and maps

高洛峰

Release： 2016-10-18 09:17:43

Original

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Unpacking is to extract each element in a sequence or map separately. A simple way to use sequence unpacking is to extract the first or first few elements and the following elements separately, for example:

first, seconde, *rest = sequence

If there are at least three elements in sequence, then after executing the above code, first == sequence[0], second == sequence[0], rest == sequence[2:].

The function receives uncertain parameters

When the parameters of the function are uncertain, you can use *args and **kwargs. *args has no key value, and **kwargs has a key value.

#!/usr/bin/python
# -*- coding:utf-8 -*-
import sys
reload(sys)
sys.setdefaultencoding(&#39;utf-8&#39;)
  
&#39;&#39;&#39;
当函数的参数不确定时，可以使用*args 和**kwargs，*args 没有key值，**kwargs有key值。
  
&#39;&#39;&#39;
  
def fun_var_args_kwargs(data1, *args, **kwargs):
    print &#39;data1:&#39;, type(data1), data1
    print &#39;*args:&#39;, type(args), args
    print &#39;**kwargs:&#39;, type(kwargs), kwargs
  
fun_var_args_kwargs(&#39;this is data1&#39;, 2, &#39;3&#39;, 4.0, k1=&#39;value1&#39;, k2=&#39;value2&#39;)
  
print &#39;-------------&#39;
  
def print_args(*args, **kwargs):
    print args.__class__.__name__, args, kwargs.__class__.__name__, kwargs
  
print_args()
print_args(1, 2, 3, a=&#39;A&#39;)

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Print results:

data1: <type &#39;str&#39;> this is data1
*args: <type &#39;tuple&#39;> (2, &#39;3&#39;, 4.0)
**kwargs: <type &#39;dict&#39;> {&#39;k2&#39;: &#39;value2&#39;, &#39;k1&#39;: &#39;value1&#39;}
-------------
tuple () dict {}
tuple (1, 2, 3) dict {&#39;a&#39;: &#39;A&#39;}

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