Stack class in Python

The LIFO structure underneath undo history and parsers.

class Stack:
    def __init__(self):
        self._items = []

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

    def pop(self):
        if not self._items:
            raise IndexError("pop from empty stack")
        return self._items.pop()

How it works

1. Backs the stack with a plain list.
2. push appends to the end.
3. pop removes the last item, raising IndexError when empty.

Keywords and builtins used here

• Stack
• class
• def
• if
• pop
• push
• raise
• return
• self

The run, in numbers

Lines

11

Characters to type

199

Tokens

58

Three-star pace

100 tpm

At the three-star pace of 100 tokens a minute, this run takes about 35 seconds.

Type this snippet

Step 5 of 5 in Classes, step 43 of 72 in Language basics.

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