Importing the same module twice

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Accepted Answer

The very first time a module is imported, Python finds and executes the file, then stores the resulting module object in sys.modules under the module's fully qualified name. Every subsequent 'import x' in any file during that process just retrieves the cached object - the file is not read or executed again. This is why module-level state (singletons, connection pools, config objects) is initialized exactly once. It also means two different files that both import the same module share the same object - if one mutates module-level state, the other sees the change.