[B10886][덱][python]

https://www.acmicpc.net/problem/10866

---

import sys
from collections import deque

n = int(sys.stdin.readline())
dq = deque()

for i in range(n):
    cmd = list(sys.stdin.readline().split())
    
    if cmd[0] == 'push_front':
        dq.appendleft(cmd[1])
        
    elif cmd[0] == 'push_back':
        dq.append(cmd[1])
        
    elif cmd[0] == "pop_front":
        if len(dq) == 0:
            print('-1')
        else:
            print(dq.popleft())
            
    elif cmd[0] == "pop_back":
        if len(dq) == 0: print('-1')
        else: print(dq.pop())
            
    elif cmd[0] == "size":
        print(len(dq))

    elif cmd[0] == "empty":
        if len(dq) == 0: print('1')
        else : print('0')

    elif cmd[0] == "front":
        if len(dq) == 0: print('-1')
        else: print(dq[0])
            
    elif cmd[0] == "back":
        if len(dq) == 0: print('-1')
        else: print(dq[len(dq)-1])