473,372 Members | 1,596 Online
Bytes | Software Development & Data Engineering Community
Post Job

Home Posts Topics Members FAQ

Join Bytes to post your question to a community of 473,372 software developers and data experts.

threads, mutual exclusion, and lists

I have two threads that share a python list. One thread adds to the
list with append(), the other thread removes items with pop().

My question is -- are python list operations atomic? If they are not,
then I assume I need to put some mutual exclusion around the append()
and pop() calls ?

Thanks,
Scott

Aug 15 '07 #1
6 3993
On Aug 15, 1:36 pm, Scott <smba...@gmail.comwrote:
I have two threads that share a python list. One thread adds to the
list with append(), the other thread removes items with pop().

My question is -- are python list operations atomic? If they are not,
then I assume I need to put some mutual exclusion around the append()
and pop() calls ?

Thanks,
Scott
You might want to consider using a Queue instead. It is designed to be
thread-safe.

Aug 15 '07 #2
I have two threads that share a python list. One thread adds to the
list with append(), the other thread removes items with pop().

My question is -- are python list operations atomic?
Yes, they are in the current implementation of CPython (all versions).
Notice that not *all* operations are atomic (e.g. .sort() is not),
but both append and pop happen to be atomic (which is primarily because
they don't need to call back to user-defined functions, unlike sort).

It's not a language property, though; things may be different in Jython
or IronPython.

Regards,
Martin
Aug 15 '07 #3
My question is -- are python list operations atomic? If they are not,
then I assume I need to put some mutual exclusion around the append()
and pop() calls ?
They are not, but there is one included in the standard library:
http://docs.python.org/dev/lib/module-Queue.html

Matt
Aug 15 '07 #4
>My question is -- are python list operations atomic? If they are not,
>then I assume I need to put some mutual exclusion around the append()
and pop() calls ?

They are not, but there is one included in the standard library:
http://docs.python.org/dev/lib/module-Queue.html
Why do you think they are not?

Regards,
Martin
Aug 16 '07 #5
Why do you think they are not?

Because they aren't. You even mentioned that a few operations that
aren't atomic. If operations are atomic it isn't necessarily because
of the design of the list, but the design of CPython. More
specifically the GIL. I don't mean to imply that you can't get a
multi-threaded app to communicate using lists, but the Queue is
explicitly built for it and better suited.

Matt
Aug 16 '07 #6
>Why do you think they are not?
>
Because they aren't. You even mentioned that a few operations that
aren't atomic.
OTOH, the OP specifically asked for .append() and .pop(), which are
atomic.

Regards,
Martin
Aug 16 '07 #7

This thread has been closed and replies have been disabled. Please start a new discussion.

Similar topics

23
by: Antoon Pardon | last post by:
I have had a look at the signal module and the example and came to the conclusion that the example wont work if you try to do this in a thread. So is there a chance similar code will work in a...
0
by: Morten Gulbrandsen | last post by:
Hello Programmers, Thank you for the kind advice, I have another small problem with MySQL I'd like to investigate, All I get is this:=20 ERROR 1005 at line 47:=20 Can't create table...
5
by: clusardi2k | last post by:
Hello, I have a assignment just thrown onto my desk. What is the easiest way to solve it? Below is a brief description of the task. There are multible programs which use the same library...
2
by: Luk Vloemans | last post by:
Hey, Having a few problems using threads in C#. In the msdn documentation, mutual exclusion is only discussed when dealing with threads that all execute the same method. What's the actual...
9
by: bonk | last post by:
Does anyone have a simple example on how to prohibit that any thread other than the current thread modifies a certain object (a collection) while we are in a certain section of the code? In other...
5
by: iLL | last post by:
So why is it that we need to use the Invoke method when updating the GUI? The following is the way we are suppose to update GUI components: delegate void textIt(object o); public partial...
167
by: darren | last post by:
Hi I have to write a multi-threaded program. I decided to take an OO approach to it. I had the idea to wrap up all of the thread functions in a mix-in class called Threadable. Then when an...
0
by: Faith0G | last post by:
I am starting a new it consulting business and it's been a while since I setup a new website. Is wordpress still the best web based software for hosting a 5 page website? The webpages will be...
0
isladogs
by: isladogs | last post by:
The next Access Europe User Group meeting will be on Wednesday 3 Apr 2024 starting at 18:00 UK time (6PM UTC+1) and finishing by 19:30 (7.30PM). In this session, we are pleased to welcome former...
0
by: taylorcarr | last post by:
A Canon printer is a smart device known for being advanced, efficient, and reliable. It is designed for home, office, and hybrid workspace use and can also be used for a variety of purposes. However,...
0
by: Charles Arthur | last post by:
How do i turn on java script on a villaon, callus and itel keypad mobile phone
0
by: aa123db | last post by:
Variable and constants Use var or let for variables and const fror constants. Var foo ='bar'; Let foo ='bar';const baz ='bar'; Functions function $name$ ($parameters$) { } ...
0
by: emmanuelkatto | last post by:
Hi All, I am Emmanuel katto from Uganda. I want to ask what challenges you've faced while migrating a website to cloud. Please let me know. Thanks! Emmanuel
0
BarryA
by: BarryA | last post by:
What are the essential steps and strategies outlined in the Data Structures and Algorithms (DSA) roadmap for aspiring data scientists? How can individuals effectively utilize this roadmap to progress...
1
by: Sonnysonu | last post by:
This is the data of csv file 1 2 3 1 2 3 1 2 3 1 2 3 2 3 2 3 3 the lengths should be different i have to store the data by column-wise with in the specific length. suppose the i have to...
0
by: Hystou | last post by:
There are some requirements for setting up RAID: 1. The motherboard and BIOS support RAID configuration. 2. The motherboard has 2 or more available SATA protocol SSD/HDD slots (including MSATA, M.2...

By using Bytes.com and it's services, you agree to our Privacy Policy and Terms of Use.

To disable or enable advertisements and analytics tracking please visit the manage ads & tracking page.