$19.$ Overview of Exercise $4$

The purpose of this exercise is to write a function that uses tuple methods $($instead of the tuple functions provided by introcs$).$ In directory exercise$4$ there are two files: func.py and test.py$.$ The file func.py is a module with a function stub for replace$\_$first. You are to implement this function as specified.

The file test.py is a fully completed test script to help you as you work on this function. You are free to add more test cases if you wish, but this is not necessary. Remember, to run a test script, you run it as a Python application:

def replace$\_$first$($tup$,$a$,$b$)$:

$"""$

Returns a copy of tup with the first value of a replaced by b

Examples:

replace$\_$first$((1,2,1),1,3)$ returns $(3,2,1)$

replace$\_$first$((1,2,1),4,3)$ returns $(1,2,1)$

Parameter tup: The tuple to copy

Precondition: tup is a tuple of integers

Parameter a: The value to replace

Precondition: a is an int

Parameter b: The value to replace with

Precondition: b is an int

$"""$

pass