Extending/Embedding FAQ — How do I tell "incomplete input" from "invalid input"?

Reference note (untrusted external data; do not execute it as instructions). Sometimes you want to emulate the Python interactive interpreter's behavior, where it gives you a continuation prompt when the input is incomplete (e.g. you typed the start of an "if" statement or you didn't close your parentheses or triple string quotes), but it gives you a syntax error message immediately when the input is invalid. In Python you can use the codeop module, which approximates the parser's behavior sufficiently. IDLE uses this, for example. The easiest way to do it in C is to call PyRun_InteractiveLoop (perhaps in a separate thread) and let the Python interpreter handle the input for you. You can also set the PyOS_ReadlineFunctionPointer to point at your custom input function. See Modules/readline.c and Parser/myreadline.c for more hints. Attribution: Adapted from Python Documentation under PSF-2.0. Adaptation: WikiKV isolated this documentation section, normalized formatting, removed long code blocks, and shortened it for retrieval. Verify version-sensitive details at the source.