CODEWITHSUNDEEP
pythontestingpython-3.xinputmocking
avimehenwal
avimehenwal

Reputation: 1592

Feeding random values to python input() pragmatically without user intervention?

I am looking to find a way to pass random values to a python code which takes multiple user inputs from the user command line from following python command. I think it could help me in testing.

num = input("Some prompt")

Is there any method/way to automatically (programatically) pass values to these python input() functions without waiting for user input on console ?

Also, my code takes multiple inputs from user based on a user input which specifies how many user inputs to fetch.

My code:

def delicious_prize(n):
    ##N no of boxes
    ##K product number of chocklates in N boxes 
    ##T total no of test cases
    print("n = ", n)
    if not isinstance(n, int):
        print("Not integer type. Only int accepted. Aborting")
        return False
    elif not n <= 1000:
        print("Inpute n: %s is not in range. Should be less than or equal to 1000"%(n))
        exit
    elif n < 0:
        print("No of boxes cannot be negative. Taking positve magnitude as %s"%(abs(n)))
        n = abs(n)
    elif n == 0:
        print("No chocklate boxes offered !")
        exit

    num_list = []
    for i in range(n):
        num = input("Enter no of chocklates in %sth box : "%(i))
        num_list.append(int(num))
    num_tuple = tuple(num_list)
    print(num_tuple)
    return tuple_count(num_tuple)


if __name__=='__main__':

    print(delicious_prize(2))
    print(delicious_prize(0))
    print(delicious_prize(-3))
    print(delicious_prize('wqete'))

Upvotes: 0

Views: 440

Answers (5)

James Johnson
James Johnson

Reputation: 91

I would rather replace sys.stdin when you are doing the testing:

import StringIO
import sys 

sys.stdin = StringIO.StringIO("1000\n")
num = input("some number: ")

print("\nread %d from input" % num)

Step through the example above at https://dbgr.cc/4u#autoPlay=true

Upvotes: 1

Wolf
Wolf

Reputation: 10238

There is a very obvious way to replace the built-in input function. Just insert two lines at the beginning of the part you dedicated to testing:

if __name__=='__main__':
    import random
    input = lambda s: random.randint(1, 12)
    print(delicious_prize(2))
    print(delicious_prize(0))
    print(delicious_prize(-3))
    print(delicious_prize('wqete'))

You asked for randomness that's why I used it - I'd probably start with a constant input:

    input = lambda s: 6

Upvotes: 1

PM 2Ring
PM 2Ring

Reputation: 55469

Another way to feed data to a program that's expecting console input is to use input redirection

You just put the data you want to input into a plain text file (eg data.txt), with one input string per line, and then you can do:

python myprog.py < data.txt

There are variations on this theme, eg feeding the output of one program into the input of another, as the Wikipedia article explains.

The main advantage of this method is that you don't have to modify myprog.py in any way, but the disadvantage is that the stuff printed by your input prompts will look a little bit weird because the data read from the file will not be echoed to the console. Also, this technique isn't as flexible as the techniques discussed by Wolf and Martijn Pieters. But it can be very handy.

Upvotes: 1

Martijn Pieters
Martijn Pieters

Reputation: 1121962

You can replace the input() function with your own. A dedicated package for doing this during testing is part of the Python standard library: unittest.mock.

In your test you'd mock input() and have it return specific values, or entirely random values:

if __name__=='__main__':
    from unittest import mock
    with mock.patch('__main__.input', create=True) as mocked_input:
        mocked_input.side_effect = ['first input', 'second input', 'third input']
        delicious_prize(3)

In the above code, a new input object is inserted into your module, masking the built-in input() function. When it is called by code in delicious_prize, each time another value from the side_effect attribute list is returned.

In this specific test, the strings are not valid numbers; your real tests would use values that can be converted to integers.

When testing, always pass in predictable values; you want your unit tests to be solid and repeatable, not fail just some of the time.

Upvotes: 3

Wolf
Wolf

Reputation: 10238

As quamrana suggested in a comment, you can pass your own input function as parameter. 

import random

def test(x, input=input): # input function, defaults to the built-in one
    v=input("Your input: ")
    print v==x

results = (3, 4)

def ran(s):
    i = random.choice(results)
    print s+str(i)
    return i

test(3, ran)
test(4, ran)
test(4)

Output (depending on random and your input) may look like this:

Your input: 4
False
Your input: 3
False
Your input: 4
True

BTW: Testability is only one reason for isolating function logic from specific ways of input and output.

Upvotes: 0

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