1push(x) -- Push element x to the back of queue.
2pop() -- Removes the element from in front of queue.
3peek() -- Get the front element.
4empty() -- Return whether the queue is empty.

1MyQueue queue = new MyQueue();
2
3queue.push(1);
4queue.push(2);  
5queue.peek();  // returns 1
6queue.pop();   // returns 1
7queue.empty(); // returns false

1# Implement the following operations of a queue using stacks.
2#
3# push(x) -- Push element x to the back of queue.
4# pop() -- Removes the element from in front of queue.
5# peek() -- Get the front element.
6# empty() -- Return whether the queue is empty.
7# Example:
8#
9# MyQueue queue = new MyQueue();
10#
11# queue.push(1);
12# queue.push(2);
13# queue.peek();  // returns 1
14# queue.pop();   // returns 1
15# queue.empty(); // returns false
16# Notes:
17#
18# You must use only standard operations of a stack -- which means only push to top, peek/pop from top, size, and is
19# empty operations are valid.
20# Depending on your language, stack may not be supported natively. You may simulate a stack by using a list or
21# deque (double-ended queue), as long as you use only standard operations of a stack.
22# You may assume that all operations are valid (for example, no pop or peek operations will be called on an empty queue).
23
24class MyQueue:
25
26    def __init__(self):
27        """
28        Initialize your data structure here.
29        """
30        self._data = []
31        self._temp_stack = []
32
33    def push(self, x):
34        """
35        Push element x to the back of queue.
36        :type x: int
37        :rtype: void
38        """
39        self._data.append(x)
40
41    def pop(self):
42        """
43        Removes the element from in front of queue and returns that element.
44        :rtype: int
45        """
46        if len(self._temp_stack) == 0:
47            while len(self._data) != 0:
48                self._temp_stack.append(self._data.pop())
49        return self._temp_stack.pop()
50
51    def peek(self):
52        """
53        Get the front element.
54        :rtype: int
55        """
56        if len(self._temp_stack) == 0:
57            while len(self._data) != 0:
58                self._temp_stack.append(self._data.pop())
59        return self._temp_stack[-1]
60
61    def empty(self):
62        """
63        Returns whether the queue is empty.
64        :rtype: bool
65        """
66        return len(self._data) == 0 and len(self._temp_stack) == 0
67
68# Your MyQueue object will be instantiated and called as such:
69# obj = MyQueue()
70# obj.push(x)
71# param_2 = obj.pop()
72# param_3 = obj.peek()
73# param_4 = obj.empty()