Python Deque Module Use detailed _python

To create a deque sequence:

From collections import deque

d = deque ()

Deque provides a list-like approach to operations:

  D = deque ()
  d.append (' 1 ')
  d.append (' 2 ')
  d.append (' 3 ')
  len (d)
  d[0]
  d[-1]

Output results:

  3
  ' 1 '
  3 '

Pop is used on both ends:

  D = deque (' 12345 ')
  len (d)
  d.popleft ()
  d.pop ()
  D

Output results:

  5
  ' 1 '
  5 '
  deque ([' 2 ', ' 3 ', ' 4 '])

We can also limit the length of the deque:

D = deque (maxlen=30)

When the deque of the limit length increases the items that exceed the limit number, the other side of the item is automatically deleted:

  D = deque (maxlen=2)
  d.append (1)
  d.append (2)
  D
  d.append (3)
  D
  deque ([1, 2], maxlen=2)
  Deque ([2, 3], maxlen=2)

Add items in list to deque:

  D = deque ([1,2,3,4,5])
  d.extendleft ([0])
  d.extend ([6,7,8])
  D

Output results:

  Deque ([0, 1, 2, 3, 4, 5, 6, 7, 8])