Is there a way in Python to simulate keyboard input to a function that asks for input?

Question

I have a function in my code that asks the user for input:

def function_1():
    ...
    x = input('Please provide input')
    ...
    return something

I want to be able to run my code, and when the program eventually reaches function_1 and asks the user for input, automatically provide it with some specified input. When unittesting, I can use the mock library to simulate keyboard input as below

@mock.patch('builtins.input', side_effects=[1,2,3])
function_1()
function_1()
function_1()

This calls the function three times and provides the inputs {1, 2, 3}. I'm wondering if there is a way to do the same thing outside of unittesting.

I'm aware that I can rewrite the code, or use pipe in terminal. But I'm more curious about whether this can be solved in the manner described above.

L3viathan · Accepted Answer · 2020-01-10 15:23:32Z

2

One way is to overwrite sys.stdin:

import sys
from io import StringIO

oldstdin = sys.stdin
sys.stdin = StringIO("1\n2\n3\n")

assert input() == "1"
assert input() == "2"
assert input() == "3"

sys.stdin = oldstdin

answered Jan 10, 2020 at 15:23

L3viathan

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Comments

Sunny Patel · Accepted Answer · 2020-01-10 15:34:28Z

1

The great thing about Python is that you can override just about any function, even built-ins.

def override():
  from itertools import count
  counter = count()
  return lambda *args, **kwargs: next(counter)
input = override()

def x():
  return input("Testing123")

print(x())  # 1
print(x())  # 2 
print(x())  # 3

Though, this has to be done before your functions are called.

answered Jan 10, 2020 at 15:34

Sunny Patel

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