标签：pass net systems lex lambda 一句话 logs span offer
说实话两年来，我从来没有如此的关注过注释，不说话先上代码
def add(a, b) -> 0:
result = a + b
add.__annotations__[‘return‘] += result
return result
print(add.__annotations__[‘return‘]) #0
add(3, 4)
print(add.__annotations__[‘return‘]) #7
add(5, 5)
print(add.__annotations__[‘return‘]) #10
这是python3.3的新的函数注释方式，不支持2，亲试
具体可以有下面三种方式
方式一： 下面的注释参数m:后面是注释，v:后面是注释，->后面是返回值
>>> def kinetic_energy(m:‘in KG‘, v:‘in M/S‘)->‘Joules‘:
... return 1/2*m*v**2
...
>>> kinetic_energy.__annotations__
{‘return‘: ‘Joules‘, ‘v‘: ‘in M/S‘, ‘m‘: ‘in KG‘}
方式二：注释可以为返回值
>>> rd={‘type‘:float,‘units‘:‘Joules‘,‘docstring‘:‘Given mass and velocity returns kinetic energy in Joules‘}
>>> def f()->rd:
... pass
>>> f.__annotations__[‘return‘][‘type‘]
<class ‘float‘>
>>> f.__annotations__[‘return‘][‘units‘]
‘Joules‘
>>> f.__annotations__[‘return‘][‘docstring‘]
‘Given mass and velocity returns kinetic energy in Joules‘
方式三：
def validate(func, locals):
for var, test in func.__annotations__.items():
value = locals[var]
try:
pr=test.__name__+‘: ‘+test.__docstring__
except AttributeError:
pr=test.__name__
msg = ‘{}=={}; Test: {}‘.format(var, value, pr)
assert test(value), msg
def between(lo, hi):
def _between(x):
return lo <= x <= hi
_between.__docstring__=‘must be between {} and {}‘.format(lo,hi)
return _between
def f(x: between(3,10), y:lambda _y: isinstance(_y,int)):
validate(f, locals())
print(x,y)
>>> f(2,2)
AssertionError: x==2; Test: _between: must be between 3 and 10
>>> f(3,2.1)
AssertionError: y==2.1; Test: <lambda>
方法总结：
1、在参数后面加注释，可以替代常规默认参数
2、函数名括号后面是返回值对应的value，相当于函数的默认返回值
3、通过__annotations__ 来获取所有的注释信息
通过上面的代码示例，开头代码就总结了几乎所有方法
def add(a:1, b:"aaa") -> 0:
result = a + b
add.__annotations__[‘return‘] += result
return result
print(add.__annotations__[‘return‘])
print(add.__annotations__.items())
add(3, 4)
print(add.__annotations__[‘return‘])
add(5, 5)
print(add.__annotations__[‘return‘])
打印结果：
0
dict_items([(‘b‘, ‘aaa‘), (‘return‘, 0), (‘a‘, 1)])
7
17
为什么这种注释方式我如此的重视？
这种逆天的注释方式，不再是常规的文本方式注释用来解释，而是以一种反射的机制来进行注释，真正做到灵活多变物尽其用
引用官方上面的一句话：
They have the potential to usher in a new era of introspective tools that help developers master more and more complex systems. They also offer the more advanced developer a standard and readable way to associate metadata directly with arguments and return value in order to create custom tools and interact with decorators.
标签：pass net systems lex lambda 一句话 logs span offer
原文地址：http://www.cnblogs.com/pyrene/p/7476617.html
