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Composite_side_effects.py
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Composite_side_effects.py
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#region Bad god logger
from abc import ABC, abstractmethod
from collections import deque
from enum import IntEnum
class LogLevel(IntEnum):
DEBUG = 1
INFO = 2
WARN = 3
ERROR = 4
#region
class BadGodLogger:
def log(self, message: str, log_level: LogLevel) -> None:
formatted_message = f"[{log_level.name}] {message}"
# stdout logging
print(formatted_message)
# File logging
with open("log.txt", "a") as log_file: # 'a' means append mode
log_file.write(formatted_message)
# Imagine 3rd logger and 4th logger and so on...
def bad_main() -> None:
logger = BadGodLogger()
logger.log("First message", LogLevel.INFO)
logger.log("second message", LogLevel.INFO)
#endregion
#region Improved logger but verbose
class ILogger(ABC):
@abstractmethod
def log(self, message: str, log_level: LogLevel) -> None:
pass
class StdoutLogger(ILogger):
def log(self, message: str, log_level: LogLevel) -> None:
print(f"[{log_level.name}] {message}")
class FileLogger(ILogger):
def log(self, message: str, log_level: LogLevel) -> None:
with open("log.txt", "a") as log_file: # 'a' means append mode
log_file.write(f"[{log_level.name}] {message}")
class DatabaseLogger(ILogger):
def log(self, message: str, log_level: LogLevel) -> None:
pass
def improved_main() -> None:
loggers: list[ILogger] = [StdoutLogger(), FileLogger()]
for logger in loggers:
logger.log("First message", LogLevel.INFO)
for logger in loggers:
logger.log("Second message", LogLevel.INFO)
#endregion
#region Good logger using Composite design pattern
class ForEachLogger(ILogger): # The Composite implementation of the interface
def __init__(self, *loggers: ILogger) -> None:
self.__loggers = loggers
def log(self, message: str, log_level: LogLevel) -> None:
for logger in self.__loggers:
logger.log(message, log_level)
class HotColdLogger(ILogger): # Important logs go to how path, others to cold path
def __init__(self, hot_path_logger: ILogger, cold_path_logger: ILogger) -> None:
self.__hot_path_logger = hot_path_logger
self.__cold_path_logger = cold_path_logger
def log(self, message: str, log_level: LogLevel) -> None:
if log_level.value >= LogLevel.WARN.value:
self.__hot_path_logger.log(message, log_level)
else:
self.__cold_path_logger.log(message, log_level)
def good_main() -> None:
logger = HotColdLogger(
hot_path_logger=ForEachLogger(
StdoutLogger(),
FileLogger()
),
cold_path_logger=ForEachLogger(
StdoutLogger(),
FileLogger(),
DatabaseLogger()
)
)
logger.log("First message", LogLevel.INFO)
logger.log("second message", LogLevel.INFO)
#endregion