1-Python - 单例模式
about
所谓单例，是指一个类的实例从始至终只能被创建一次，并且对外部提供一个访问它的全局访问点。
优点
- 对唯一实例的受控访问。
- 单例相当于全局变量，但不会给命名空间造成污染。
在Python中，实现单例模式的方式有多种。
基于__new__实现
class Singleton(object):
def __new__(cls, *args, **kwargs):
if not hasattr(cls, '_instance'):
cls._instance = super(Singleton, cls).__new__(cls)
return cls._instance
def __init__(self, num):
self.num = num
num1 = Singleton(10)
num2 = Singleton(20)
print(num1.num, num2.num) # 20 20
print(id(num1), id(num2)) # 2467135043848 2467135043848
示例：
import logging
class LoggerHandler:
def __new__(cls, *args, **kwargs):
if not hasattr(cls, '_instance'):
cls._instance = super(LoggerHandler, cls).__new__(cls)
return cls._instance
def __init__(self, log_name, log_level, file_path, stream_level='info', file_level='warning'):
self.logger_name = log_name
self.logger_level = log_level
self.file_path = file_path
self.stream_level = stream_level
self.file_level = file_level
# 创建日志对象
self.logger = logging.getLogger(self.logger_name)
# 设置默认日志级别
self.logger.setLevel(self.logger_level)
# 设置日志输出流
to_stream = logging.StreamHandler()
to_file = logging.FileHandler(self.file_path)
# 设置日志输出级别
to_stream.setLevel(self.stream_level)
to_file.setLevel(self.file_level)
# 设置日志输出格式
formatter = logging.Formatter("%(asctime)s %(name)s %(levelname)s %(message)s")
to_stream.setFormatter(formatter)
to_file.setFormatter(formatter)
self.logger.addHandler(to_stream)
self.logger.addHandler(to_file)
log = LoggerHandler(
log_name='log',
log_level=logging.INFO,
file_path='./log.log',
stream_level=logging.INFO,
file_level=logging.WARNING
)
log.logger.info('info')
log.logger.error('error')
log.logger.warning('warning')
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