Rodrigo Girão Serrão: TIL #139 – Multiline input in the REPL

The text explains a method for achieving multiline input within a Python Read-Eval-Print Loop (REPL). Standard input can be accessed using `open(0)`, enabling multiline input using Ctrl+D (Unix) or Ctrl+Z (Windows) for EOF. The initial use of `open(0).read()` successfully captures multiline input as a string. However, subsequent attempts to read from standard input in this manner result in an `OSError`. This error occurs because Python closes the file descriptor after the first read operation. The solution lies in the `closefd=False` argument within the `open()` function. By setting `closefd=False`, the file descriptor remains open after reading. This allows for repeated reading of multiline input from standard input within the REPL environment. Sequential calls of `open(0, closefd=False).read()` then work without issue. This technique enables continued multiline input within the REPL session. The primary advantage is facilitating interactive code testing with multiline data.