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About a hole in Python -- reload causes module reset

編輯：Python

In many cases, we need to dynamically introduce a library , For example, we need to introduce a library on both the server and the client , Their file names are the same , How to cache them at runtime ？
Here is an interesting example , The file structure is as follows ：

# testlib1/testModulenum = 1

# testlib2/testModulenum = 2

# -*- coding: utf-8 -*-# At this point, there is a requirement as follows # We need to introduce two files with the same file name python file # And cannot be static import Only code dynamic can be called reloadimport importlibimport osimport sys# situation 1class loadModuleCS(object): """ Import the server and client Libraries """ def __init__(self): super(loadModuleCS, self).__init__() self.clientModule = None self.serverModule = None self.loadClientModule() self.loadServerModule() def _loadModule(self, path): """ load path Module under """ name = os.path.basename(path) path = path.replace(name, "") sys.path.insert(0, path) module = importlib.import_module(name.split('.')[0]) importlib.reload(module) print(" In the database num by ： ", module.num) sys.path.pop(0) return module def loadClientModule(self): path = r"F:\PythonXSLWorkSpace\PythonBaseUse\pythonBug\1error\testlib1\testModule.py" self.clientModule = self._loadModule(path) def loadServerModule(self): path = r"F:\PythonXSLWorkSpace\PythonBaseUse\pythonBug\1error\testlib2\testModule.py" self.serverModule = self._loadModule(path)loader = loadModuleCS()print(loader.clientModule.num)print(loader.serverModule.num)

reflection

The running result is as above , Think about a thing ： The library is correct when we import , Then why do we reintroduce clientModule and serverModule Take it out and take the value inside , But it's wrong ？
Let's do one thing ：

loader = loadModuleCS()print(loader.clientModule.num)print(loader.serverModule.num)print(loader.clientModule is loader.serverModule)

The results are as follows ：

Now it's clear at a glance , At this time they are actually the same thing ！ in other words clientModule and serverModule Currently, it refers to the same object ！！why？？？？？
We all know ,python The imported libraries are stored in sys.modules in , sys.modules It's a dictionary , The imported modules are stored , Could this be the reason ？

verification

class loadModuleCS(object): """ Import the server and client Libraries """ def __init__(self): super(loadModuleCS, self).__init__() self.clientModule = None self.serverModule = None self.loadClientModule() self.loadServerModule() def _loadModule(self, path): """ load path Module under """ name = os.path.basename(path) path = path.replace(name, "") sys.path.insert(0, path) module = importlib.import_module(name.split('.')[0]) importlib.reload(module) print(" In the database num by ： ", module.num) print(sys.modules["testModule"]) sys.path.pop(0) return module def loadClientModule(self): path = r"F:\PythonXSLWorkSpace\PythonBaseUse\pythonBug\1error\testlib1\testModule.py" self.clientModule = self._loadModule(path) def loadServerModule(self): path = r"F:\PythonXSLWorkSpace\PythonBaseUse\pythonBug\1error\testlib2\testModule.py" self.serverModule = self._loadModule(path)loader = loadModuleCS()print(sys.modules["testModule"])print(loader.clientModule.num)print(loader.serverModule.num)print(loader.clientModule is loader.serverModule)print(loader.clientModule is sys.modules["testModule"], loader.serverModule is sys.modules["testModule"])

The output is as follows

It proves our conjecture , here clientModule and serverModule Currently, it refers to the same object

Revise the plan

 def _loadModule(self, path): """ load path Module under """ name = os.path.basename(path) path = path.replace(name, "") sys.path.insert(0, path) moduleName = name.split('.')[0] if moduleName in sys.modules: sys.modules.pop(moduleName) module = importlib.import_module(moduleName) importlib.reload(module) print(" In the database num by ： ", module.num) print(sys.modules["testModule"]) sys.path.pop(0) return module

This is what we expected , clientModule and serverModule Reference to two different libraries ！