Print the state

Print the contents of the stack and queue.

Print the state

In the last step we print the current state of the stack. This lets the user see the undo history and adds transparency.

To print the whole stack a loop or direct print(stack) is used. The contents are listed from bottom to top.

This is the final piece of the project; all functions work together to form a complete undo system.

State report

Printing the state lets the user see the undo history. The whole stack is listed; the first action at the bottom, the last at the top.

This shows the user what can be undone. It is also useful for debugging; it confirms the stack grows correctly.

In real text editors this is shown in a side panel.

Exercise Print state

Write print_state(stack). Print the stack contents. Print ['ekle', 'sil'] with s = init_undo(); push_undo(s, 'ekle'); push_undo(s, 'sil'); print_state(s).

Show example solution

def init_undo():
    # Empty undo stack
    return []
def push_undo(stack, action):
    # Push to undo stack
    stack.append(action)
    return stack
def pop_undo(stack):
    # Pop from undo stack
    if not stack:
        return 'boş'
    return stack.pop()
def print_state(stack):
    # Print state
    print(stack)
s = init_undo()
push_undo(s, 'add')
push_undo(s, 'del')
print_state(s)

Test yourself

Print the state: match the terms

init_undo

Empty stack
push_undo

Push
pop_undo

Undo
print_state

Print
What is done to see the stack state?
- print(stack)
- append(stack)
- sort(stack)
- pop(stack)
Show answer

print(stack) — print(stack)
Printing
```
print(____)
```
Show answer
```
print(stack)
```

Next lesson: What is a graph?

We Are Enhancing Your Experience

Cookie Preferences

Strictly Necessary Cookies

Analytical Cookies