Using a library that when I call a certain function that I will call foo() , I am prompted for input as such:

def foo():
   if input("Proceed?") == 'yes':
        take_action()

I am required to pass in an answer to continue.

But I would like to be able to loop over foo() with a default value to feed the prompt.

The problem is the developers did not provide an option to supply a default value for the prompt.

Ideally they would have written foo() like this:

def foo(default_response=None):
    if default_response == 'yes':
        take_action()
    elif input("Proceed?") == 'yes':
        take_action()

Given that they did not supply an option for a default response, is there a way for me to loop over foo() and provide the input automatically without changing the source code?

CodePudding user response：

One solution is to monkey patch the library to temporarily replace the input function. For example, if I have module foo.py that looks like this:

def take_action():
    print("doing something")


def foo():
    if input("Proceed? ") == "yes":
        take_action()

I can write bar.py like this:

import foo
from unittest import mock


def fake_input(default_response=None):
    '''Creates a replacement for the `input` function that will
    return a default response if one was provided.'''

    def _input(prompt):
        return default_response if default_response else input(prompt)

    return _input


with mock.patch("foo.input", new=fake_input("yes")):
    foo.foo()

foo.foo()

If you run this code, you'll see that the first call to foo.foo() uses a default input, and proceeds without prompting. The second call to foo.foo() will prompt normally.