How do I implement a circular buffer in Python?

Question

I have a matrix for instance

a=[12,2,4,67,8,9,23]

and I would like a code that appends a value say 45 to it and removes the first value '12' so in essence I want to make

a = [2,4,67,8,9,23,45]

I want to work with regular matrices not numpy matrices so I can't use hstack or vstack How do I do this in python? Any help would be appreciated, thanks

This is not a sliding window; this is a circular buffer.

Martijn Pieters
– Martijn Pieters

2012-11-29 15:13:48 +00:00
Commented Nov 29, 2012 at 15:13 — Martijn Pieters
– Martijn Pieters, Commented Nov 29, 2012 at 15:13

FogleBird · Accepted Answer · 2012-11-29 15:11:41Z

13

Use a deque.

http://docs.python.org/2/library/collections.html#collections.deque

>>> import collections
>>> d = collections.deque(maxlen=7)
>>> d.extend([12,2,4,67,8,9,23])
>>> d.append(45)
>>> print d
deque([2, 4, 67, 8, 9, 23, 45], maxlen=7)

answered Nov 29, 2012 at 15:11

FogleBird

77.3k25 gold badges133 silver badges136 bronze badges

Sign up to request clarification or add additional context in comments.

4 Comments

user17151 Over a year ago

Thanks but what does deque mean? And thanks for the answer but I think I will go with Marian's answers it is simpler

glglgl Over a year ago

@user17151 deque = double-ended queue. If you have 20 values, it doesn't matter which you use. If you have 2 million values, the deque is the qay to go rather than a mere list.

FogleBird Over a year ago

@user17151: that's fine but a deque is more efficient since it won't have to copy the entire data structure each time an element is appended.

Sam Mussmann Over a year ago

This makes the append operation more efficient, but accessing elements in the middle of the data structure is less efficient with a deque than with a list (O(n) vs O(1)).

jaho · Accepted Answer · 2012-11-29 15:13:28Z

3

The simplest way:

a = a[1:] + [45]

edited Nov 29, 2012 at 15:13

answered Nov 29, 2012 at 15:12

jaho

5,0426 gold badges43 silver badges68 bronze badges

2 Comments

user17151 Over a year ago

This is brilliant. Should have thought of it, I'm just a beginner in python. Thanks a lot

jaho Over a year ago

No problem, but FogleBird's answer is in fact more efficient if performance is a concern at all.

PTEC Productions · Accepted Answer · 2012-11-29 15:18:41Z

1

You can do this:

a=[12,2,4,67,8,9,23]
a.append(45)
a.pop(0)

answered Nov 29, 2012 at 15:18

PTEC Productions

1475 bronze badges

Collectives™ on Stack Overflow

How do I implement a circular buffer in Python?

3 Answers 3

4 Comments

2 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

4 Comments

2 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related