Примеры декораторов с аргументами

В Flask декораторы используются для сопоставления функция с ссылками на сайте:

url_function_map = {}

def register(route):
    def decorator(func):
        url_function_map[route] = func
        return func
    return decorator

@register('/')
def func(a,b):
    return a+b

@register('/scripts')
def func2(a,b):
    return a+b


In [3]: url_function_map
Out[3]: {'/': <function __main__.func>, '/scripts': <function __main__.func2>}

А также для ограничения доступа к определенным ссылкам:

from functools import wraps


class User:
    def __init__(self, username, permissions=None):
        self.username = username
        self.permissions = permissions

    def has_permission(self, permission):
        return permission in self.permissions


natasha = User('nata', ['admin', 'user'])
oleg = User('oleg', ['user'])

current_user = natasha


class AccessDenied(Exception):
    pass


def permission_required(permission):
    def decorator(func):
        @wraps(func)
        def decorated_function(*args, **kwargs):
            if not current_user.has_permission(permission):
                raise AccessDenied('You shall not pass!')
            return func(*args, **kwargs)
        return decorated_function
    return decorator


@permission_required('admin')
def secret_func():
    return 42


In [77]: secret_func()
Out[77]: 42

In [78]: current_user = oleg

In [79]: secret_func()
---------------------------------------------------------------------------
AccessDenied                              Traceback (most recent call last)
<ipython-input-79-23f2f66c4b3b> in <module>()
----> 1 secret_func()

<ipython-input-75-240afbb2dcfe> in decorated_function(*args, **kwargs)
      4         def decorated_function(*args, **kwargs):
      5             if not current_user.has_permission(permission):
----> 6                 raise AccessDenied('You shall not pass!')
      7             return func(*args, **kwargs)
      8         return decorated_function

AccessDenied: You shall not pass!

Иногда в зависимости от типа аргумента надо вызываться разные функции:

from netmiko import ConnectHandler
import yaml
from pprint import pprint


def send_show_command(device, show_command):
    with ConnectHandler(**device) as ssh:
        ssh.enable()
        result = ssh.send_command(show_command)
    return result

def send_config_commands(device, config_commands):
    with ConnectHandler(**device) as ssh:
        ssh.enable()
        result = ssh.send_config_set(config_commands)
    return result

def send_commands(device_list, config=None, show=None):
    if show:
        return send_show_command(device_list, show)
    elif config:
        return send_config_commands(device_list, config)



if __name__ == "__main__":
    commands = [ 'logging 10.255.255.1',
                 'logging buffered 20010',
                 'no logging console' ]
    show_command = "sh ip int br"
    with open('devices.yaml') as f:
        dev_list = yaml.safe_load(f)

    send_commands(dev_list, config=commands)
    send_commands(dev_list, show=show_command)

В стандартной библиотеке есть интересный декоратор singledispatch:

from netmiko import ConnectHandler
import yaml
from pprint import pprint
from functools import singledispatch
from collections.abc import Iterable, Sequence


@singledispatch
def send_commands(command, device):
    print('original func')
    raise NotImplementedError('Поддерживается только список или строка')

@send_commands.register(str)
def _(show_command, device):
    print('Выполняем show')
    with ConnectHandler(**device) as ssh:
        ssh.enable()
        result = ssh.send_command(show_command)
    return result

@send_commands.register(Iterable)
def _(config_commands, device):
    print('Выполняем config')
    with ConnectHandler(**device) as ssh:
        ssh.enable()
        result = ssh.send_config_set(config_commands)
    return result

if __name__ == "__main__":
    commands = ['logging 10.255.255.1',
                'logging buffered 20010',
                'no logging console' ]
    show_command = "sh ip int br"

    with open('devices.yaml') as f:
        r1 = yaml.safe_load(f)[0]

    print(send_commands(tuple(commands), r1))
    print(send_commands(show_command, r1))