3 ms·

> dynamically redefine functions even to violate lexical scoping When would someone want to do this?

• JulianChastain 2y ago
  Let's say you had a library function foo, which takes no arguments, does an expensive computation, and then prints a single result to the console. You need the function to instead return the value, so that you can do more computation on it. You could write a wrapper function that will call foo, but replace the print function with one that records the printed result. For example: def foo(): print('usually this value is inaccessible from "python land"') def extract_printed_values(bar): global print old_print, returnv = print, None def new_print(x): nonlocal returnv old_print(returnv := x) print = new_print bar() print = old_print return returnv fooval = extract_printed_values(foo) fooval will then be equal to whatever value foo printed to the console, otherwise foo will behave exactly the same as normal (assuming it only printed a single value), and print will even behave normally afterwards