class list(list):
    def __init__(self, arg):
        super().__init__(arg)
        
    def replace_one(self, old:object, new:object, index:int=None) -> list:
        self = self.copy()
        self[self.index(old) if index == None else index] = new
        return self
    
    def replace_all(self, old:object, new:object) -> list:
        self = self.copy()
        for i in enumerate(self):
            if i[1] == old:
                self[i[0]] = new
        
        return self
    
mylist = list("Pysources")
print(mylist)
# Output -> ['P', 'y', 's', 'o', 'u', 'r', 'c', 'e', 's']

replace_one = mylist.replace_one("P", "p")
print(replace_one)
# Output -> ['p', 'y', 's', 'o', 'u', 'r', 'c', 'e', 's']

replase_all = mylist.replace_all("s", "S")
print(replase_all)
# Output -> ['P', 'y', 'S', 'o', 'u', 'r', 'c', 'e', 'S']