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70 lines
1.9 KiB
Python
70 lines
1.9 KiB
Python
from __future__ import print_function
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__author__ = 'Omkar Pathak'
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class Stack(object):
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""" A stack is an abstract data type that serves as a collection of
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elements with two principal operations: push() and pop(). push() adds an
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element to the top of the stack, and pop() removes an element from the top
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of a stack. The order in which elements come off of a stack are
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Last In, First Out (LIFO).
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https://en.wikipedia.org/wiki/Stack_(abstract_data_type)
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"""
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def __init__(self, limit=10):
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self.stack = []
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self.limit = limit
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def __bool__(self):
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return not bool(self.stack)
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def __str__(self):
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return str(self.stack)
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def push(self, data):
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""" Push an element to the top of the stack."""
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if len(self.stack) >= self.limit:
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raise StackOverflowError
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self.stack.append(data)
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def pop(self):
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""" Pop an element off of the top of the stack."""
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if self.stack:
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return self.stack.pop()
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else:
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raise IndexError('pop from an empty stack')
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def peek(self):
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""" Peek at the top-most element of the stack."""
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if self.stack:
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return self.stack[-1]
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def is_empty(self):
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""" Check if a stack is empty."""
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return not bool(self.stack)
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def size(self):
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""" Return the size of the stack."""
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return len(self.stack)
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class StackOverflowError(BaseException):
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pass
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if __name__ == '__main__':
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stack = Stack()
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for i in range(10):
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stack.push(i)
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print('Stack demonstration:\n')
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print('Initial stack: ' + str(stack))
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print('pop(): ' + str(stack.pop()))
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print('After pop(), the stack is now: ' + str(stack))
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print('peek(): ' + str(stack.peek()))
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stack.push(100)
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print('After push(100), the stack is now: ' + str(stack))
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print('is_empty(): ' + str(stack.is_empty()))
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print('size(): ' + str(stack.size()))
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