Reliability: Path/Cut Vector Technique in Python

Question

I have a list, lst, that contains only 0's and 1's of length n.

The list represents either a cut vector or a path vector, from reliability analysis, which may or may not be minimal cut/path vectors themselves.

The elements within the list represent separate variables, say x1, x2, and x3 and the length of the list, n, represents the number of variables being represented.

For example, the list [0, 1, 1] represents 3 variables, x1, x2, and x3.

Given the input, lst, I want to return a list or string that is guided by the following rules.

Rules:

1. If x_i = 1:

   a. return (x_i)

2. else if x_i = 0:

   b. return: (1 - x_i)

Examples:

[0, 1] => [1-X1, X2] or "1-X1, X2"

[1, 0] => [X1, 1-X2] or "X1, 1-X2"

[0, 1, 1] => [1-X1, X2, X3] or "1-X1, X2, X3"

[1, 1, 1] => [X1, X2, X3] or "X1, X2, X3"

My Code:

def get_function(path_vector):
    lst = []
    for item in path_vector:
        if "0" in item:
            print("1-", item, sep="")
            lst.extend(["1-", item])
        else:
            print(item)
            lst.append(item)
    print(lst)
    expr = "*".join(lst)
    return expr

Goal:

The eventual goal is to join the items in the new list - separated by a * - and input them into a function from the sympy library.

Any tips are appreciated.

Answer 1

item has values 0 or 1 but you need its position on list to create string 1-X{position} or X{position}

You may use enumarate(..., 1) to get its position on list.

Because you have integer values then you should compare integers if item == 0:

---

Minimal working code which use list examples to generate string and compare with expected result

def get_function(path_vector):
    lst = []

    for position, item in enumerate(path_vector, 1):
        if item == 0:
            text = f"1-X{position}" 
        else:
            text = f"X{position}" 
        lst.append(text)
        print('text:', text)

    print('lst:', lst)
    expr = "*".join(lst)

    return expr
    
# --- main --- 
    
examples = [    
    ([0, 1], "1-X1*X2"),
    ([1, 0], "X1*1-X2"),
    ([0, 1, 1], "1-X1*X2*X3"),
    ([1, 1, 1], "X1*X2*X3"),
]

for data, expected_result in examples:
    result = get_function(data)
    print(data, expected_result, result, expected_result==result)