A brief description of Python Console backend in PyCharm:

There are 4 main types of consoles in PyCharm:

1. Python Console (a separate tool window)

a. IPython implementation b. General Python implementation

2. Debug Console (console attached to the current debug session)

a. IPython implementation b. General Python implementation

IPython implementation is available only if ipython installed on interpreter and an option "Use IPython if available" enabled. Each of these consoles has its own implementation inside pydevd module.

1. Python Console (a separate tool window)

Entry point is pydevd/pydevconsole.py. After console launching, backend creates an instance of InterpreterInterface.

1a. If IPython is available, IPythonInterpreterInterface is imported from _pydev_bundle.pydev_ipython_console. Instance of IPythonInterpreterInterface has an attribute self.interpreter (instance of _PyDevIPythonFrontEnd) - an instance of actual interpreter, which performs actual operations like code execution, variables update or runtime completion variants calculation.

1b. If IPython isn't available, console uses InterpreterInterface declared in pydevconsole.py. It stores an instance of InteractiveConsole from built-in module code (or IronPythonInteractiveConsole for IronPython) in self.interpreter attribute and uses it code execution.

2. Debug Console

Debug Console always exists in the context of a debug process. IDE side sends command CMD_CONSOLE_EXEC to debugger backend, which then passes expression to pydevd_console_integration.console_exec(). Before the first execution request, PyCharm initializes instance of interpreter and stores it as a builtin attribute (see pydevd_console_integration.get_code_executor()). Each command executed in Debug Console is passed into pydevd_console_integration.console_exec() function.

2a. If IPython is available, CodeExecutor is imported from _pydev_bundle.pydev_ipython_code_executor. Similar to IPythonInterpreterInterface, IPythonCodeExecutor has a self.interpreter attribute, which contains an instance of _PyDevIPythonFrontEnd. Command executions and variables update are delegated to self.interpreter.

2b. If IPython isn't available, console uses CodeExecutor declared in _pydevd_bundle.pydevd_console_integration. Similar to InterpreterInterface, CodeExecutor has a self.interpreter attribute, which stores an instance of InteractiveConsole from built-in module code. Important difference from 1b is that it doesn't delegate code execution to InteractiveConsole, but uses built-in exec() function and updates variables manually.

Debug Console uses CMD_GET_COMPLETIONS command for getting runtime completion. Important note: code from pydevd_console.py is used only by PyDev, but not by PyCharm.