# Stack with Integers
 
class Stack:
    def __init__(self):
        self.items = []

    def push(self, item):
        self.items.append(item)

    def pop(self):
        if not self.is_empty():
            return self.items.pop()
        return None

    def is_empty(self):
        return len(self.items) == 0

    def __str__(self):
        return str(self.items)

    def __repr__(self):
        return f"Stack({self.items})"

int_stack = Stack()
int_stack.push(1)
int_stack.push(2)
int_stack.push(3)
print(int_stack)  
print(int_stack.pop())  
print(int_stack)  
print(int_stack.pop())  
print(int_stack)  
print(int_stack.pop())  
print(int_stack)

# Stack with Strings

class StringStack:
    def __init__(self):
        self.items = []

    def push(self, item):
        self.items.append(item)

    def pop(self):
        if not self.is_empty():
            return self.items.pop()
        return None

    def is_empty(self):
        return len(self.items) == 0

    def __str__(self):
        return str(self.items)

    def __repr__(self):
        return f"StringStack({self.items})"

str_stack = StringStack()
str_stack.push("apple")
str_stack.push("banana")
str_stack.push("cherry")
print(str_stack)  
print(str_stack.pop())  
print(str_stack)  
print(str_stack.pop())  
print(str_stack)  
print(str_stack.pop())  
print(str_stack)

# Stack with Dictionaries (Healthcare Data)

class DictStack:
    def __init__(self):
        self.items = []

    def push(self, item):
        self.items.append(item)

    def pop(self):
        if not self.is_empty():
            return self.items.pop()
        return None

    def is_empty(self):
        return len(self.items) == 0

    def __str__(self):
        return str(self.items)

    def __repr__(self):
        return f"DictStack({self.items})"

healthcare_stack = DictStack()
healthcare_stack.push({"patient_id": 1, "name": "John Doe", "age": 30})
healthcare_stack.push({"patient_id": 2, "name": "Jane Smith", "age": 25})
print(healthcare_stack)  
print(healthcare_stack.pop())  
print(healthcare_stack) 
print(healthcare_stack.pop())  
print(healthcare_stack) 
print(healthcare_stack.pop())  
print(healthcare_stack)

# Generic Stack

class GenericStack:
    def __init__(self):
        self.items = []

    def push(self, item):
        self.items.append(item)

    def pop(self):
        if not self.is_empty():
            return self.items.pop()
        return None

    def is_empty(self):
        return len(self.items) == 0

    def __str__(self):
        return str(self.items)

    def __repr__(self):
        return f"GenericStack({self.items})"

generic_stack = GenericStack()
generic_stack.push(1)
generic_stack.push("apple")
generic_stack.push({"key": "value"})
print(generic_stack)  
print(generic_stack.pop()) 
print(generic_stack)  
print(generic_stack.pop()) 
print(generic_stack)  
print(generic_stack.pop()) 
print(generic_stack)