The old way, manually logging
import logging
logger = logging.getLogger(__name__)
def func(*args, **kwargs):
logger.info(f'Call func with {args, kwargs}')
func(1, 2, 3, a=True, b='arg')
INFO:__main__:Call func with ((1, 2, 3), {'a': True, 'b': 'arg'})
1. Use decorators
For Function
def func_logger(func):
def inner(*args, **kwargs):
ret = func(*args, **kwargs)
logger.info(f'Call func {func.__name__} with {args, kwargs} returns {ret}')
return ret
return inner
@func_logger
def add(a, b):
return a + b
add(1,2)
add(1, b=2)
add(a=1, b=2)
INFO:__main__:Call func add with ((1, 2), {}) returns 3
INFO:__main__:Call func add with ((1,), {'b': 2}) returns 3
INFO:__main__:Call func add with ((), {'a': 1, 'b': 2}) returns 3
For Method
We need care of self .
def method_logger(method):
def inner(self, *args, **kwargs):
ret = method(self, *args, **kwargs)
logger.info(f'Call method {method.__name__} of {self} with {args, kwargs} returns {ret}')
return ret
return inner
class A:
a:int
def __init__(self, a):
self.a = a
@method_logger
def addX(self, x: int):
return self.a + x
def __repr__(self):
return f'A(a={self.a})'
a = A(1)
a.addX(2)
a.addX(x=3)
INFO:__main__:Call method addX of A(a=1) with ((2,), {}) returns 3
INFO:__main__:Call method addX of A(a=1) with ((), {'x': 3}) returns 4
You'd better define custom __str__ or __repr__ method for your class to describe the object in log. One simple way is using dataclass.
from dataclasses import dataclass
@dataclass
class Account:
uid: str
banlance: int
@method_logger
def transerTo(self, target: 'Account', value:int):
self.banlance -= value
target.banlance += value
return self, target
a = Account('aaaa', 10)
b = Account('bbbb', 10)
a.transerTo(b, 5)
INFO:__main__:Call method transerTo of Account(uid='aaaa', banlance=5) with ((Account(uid='bbbb', banlance=15), 5), {}) returns (Account(uid='aaaa', banlance=5), Account(uid='bbbb', banlance=15))
2. Use __getattribute__ method
def method_logger_x(method, obj):
def inner(*args, **kwargs):
ret = method(*args, **kwargs)
logger.info(f'Call method {method.__name__} of {obj} with {args, kwargs} returns {ret}')
return ret
return inner
class MethodLogger:
def __getattribute__(self, key):
value = super().__getattribute__(key)
if callable(value) and not key.startswith('__'):
return method_logger_x(value, self)
return value
@dataclass
class Account(MethodLogger):
uid: str
banlance: int
frozen: bool = False
def transerTo(self, target: 'Account', value:int):
self.banlance -= value
target.banlance += value
return self, target
def freeze(self, reason:str):
self.frozen = True
a = Account('aaaa', 10)
b = Account('bbbb', 10)
a.transerTo(b, 5)
a.freeze('Dangerous Action')
INFO:__main__:Call method transerTo of Account(uid='aaaa', banlance=5, frozen=False) with ((Account(uid='bbbb', banlance=15, frozen=False), 5), {}) returns (Account(uid='aaaa', banlance=5, frozen=False), Account(uid='bbbb', banlance=15, frozen=False))
INFO:__main__:Call method freeze of Account(uid='aaaa', banlance=5, frozen=True) with (('Dangerous Action',), {}) returns None
PS When call __getattribute__ method of a object, the value(method) has already get the self parameter.
3. Use meta class
def method_logger(method):
def inner(self, *args, **kwargs):
ret = method(self, *args, **kwargs)
logger.info(f'Call method {method.__name__} of {self} with {args, kwargs} returns {ret}')
return ret
return inner
from typing import Tuple
class MethodLoggerMeta(type):
def __new__(self, name:str, bases:Tuple[type], attrs:dict):
attrs_copy = attrs.copy()
for key, value in attrs.items():
if callable(value) and not key.startswith('__'):
attrs_copy[key] = method_logger(value)
return type(name, bases, attrs_copy)
@dataclass
class Account(metaclass=MethodLoggerMeta):
uid: str
banlance: int
frozen: bool = False
def transerTo(self, target: 'Account', value:int):
self.banlance -= value
target.banlance += value
return self, target
def freeze(self, reason:str):
self.frozen = True
a = Account('aaaa', 10)
b = Account('bbbb', 10)
a.transerTo(b, 5)
Conclusion
Adding more logs is usallay a better way. You can choose one of the three approaches you like.
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