3个超有用的Python编程小技巧

>>> 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}