class
deque:
def
__init__
(
self
)
:
self
._data
=
[
]
def
add_front
(
self
,
i
)
:
self
._data.
insert
(
0
,
i
)
def
add_back
(
self
,
i
)
:
self
._data.
append
(
i
)
def
remove_front
(
self
)
:
return
self
._data.
pop
(
0
)
def
remove_back
(
self
)
:
return
self
._data.
pop
(
)
def
front
(
self
)
:
return
self
._data
[
0
]
def
back
(
self
)
:
return
self
._data
[
-
1
]
def
is_empty
(
self
)
:
return
len
(
self
._data
)
==
0
def
__str__
(
self
)
:
return
self
._data.
__str__
(
)