function values are not printing

When I execute this code it doesn't print 'current stack numbers []' values.

But when I Uncomment the #s = c() it works, what is the reason?

def c():
    stack = []
    return stack


def check_empty(stack):
    return len(stack) == 0



def push(stack, item): 
    stack.append(item) 
    print("pushed item" + item)


def pop(stack):
    if (check_empty(stack)): 
        return "stack is emtpy"

    return stack.pop()

#s = c()

push(c(), str(1))
push(c(), str(2))
push(c(), str(3))

print("popped item" , pop(c())) 
print("current stack numbers" + str(c()))

Given that your function c() returns an empty list, the last lines of your code becomes

push([], str(1))
push([], str(2))
push([], str(3))

print("popped item" , pop([])) 
print("current stack numbers" + str([]))

Which will print nothing, as expected.

However, if you set the output from c() to a variable and push/pop to it, you will get the expected behaviour

s = c()

push(s, str(1))  # c = ["1"]
push(s, str(2))  # c = ["1", "2"]
push(s, str(3))  # c = ["1", "2", "3"]

print("popped item" , pop(s))  # prints "popped item3"
print("current stack numbers" + str(s))  # prints "current stack numbers['1', '2']