3个 Python 编程技巧

>>> xs = {'a': 4, 'b': 3, 'c': 2, 'd': 1} 
>>> for k,v in xs.items():#遍历字典 
...     print(k,v) 
... 
a 4 
b 3 
c 2 
d 1 
>>> new_order = sorted(xs.items(), key=lambda x: x[1]) #对字典的键值对列表排序 
 
>>> new_xs = { k : v for k,v in new_order} #有序列表插入新的字典 
>>> new_xs 
{'d': 1, 'c': 2, 'b': 3, 'a': 4} 
>>> for k,v in new_xs.items(): ##新字典的输出就是有序的 
...     print(k,v) 
... 
d 1 
c 2 
b 3 
a 4 

>>> import operator 
>>> sorted(xs.items(), key=operator.itemgetter(1)) 
[('d', 1), ('c', 2), ('b', 3), ('a', 4)] 

x, y, z = 0, 1, 0 
 
if x == 1 or y == 1 or z == 1: 
    print('passed') 

if 1 in (x, y, z): 
    print('passed') 
 
if x or y or z: 
    print('passed') 
 
if any((x, y, z)): 
    print('passed') 

>>> any(['a',(2,4),3,True])  
True 
>>> any(['a',(2,4),3,False]) 
True 
>>> any(['a',(),3,False])    
True 
>>> any(['',(),0,False])  
False 
>>> any(('a',(),3,False)) 
True 
>>> any(('',(),0,False))  
False 

## 注意空的可迭代对象返回 False 
>>> any(()) 
False 
>>> any([]) 
False 
>>> any('') 
False 
>>> any({}) 
False 

>>> all(['a',(2,4),1,True]) //list都为"真" 
True 
>>> all(['a',(),1,True])   //list元素中有空tuple 
False 
>>> all(['a',(2,4),0,True]) 
False 
>>> all(['a',(2,4),3,False]) 
False 
   
## 注意空的可迭代对象返回 True 
>>>all([]) 
True  
>>> all(()) 
True 
>>> all({}) 
True 
>>> all('') 
True 

>>> help(all) 
Help on built-in function all in module __builtin__: 
 
all(...) 
    all(iterable) -> bool 
 
    Return True if bool(x) is True for all values x in the iterable. 
    If the iterable is empty, return True. 
    

>>> x = {'a': 1, 'b': 2} 
>>> y = {'b': 3, 'c': 4} 
 
>>> z = {**x, **y} 
 
>>> z 
{'c': 4, 'a': 1, 'b': 3} 

>>> z = dict(x, **y) 
>>> z 
{'a': 1, 'c': 4, 'b': 3}