Is there an explainer on the difference between?  aL, bL = [[], []] xL, yL = [[]] * 2   Superficially, they should be the same.  [[], []] == [[]] * 2 True   But they behave differently.   aL.append("a") xL.append("x") bL [] yL ['x']
I needed to create a list of lists in Python, so I typed the following: my_list = [[1] * 4] * 3  The list looked like this: [[1, 1, 1, 1], [1, 1, 1, 1], [1, 1, 1, 1]]    Then I changed one of the innermost values: my_list[0][0] = 5  Now my list looks like this: [[5, 1, 1, 1], [5, 1, 1, 1], [5, 1, 1, 1]]    which is not what I wanted or expected. Can someone please explain what's going on, and how to get around it?
I need a command that will wait for a process to start accepting requests on a specific port.    Is there something in linux that does that?  while (checkAlive -host localhost -port 13000 == false)   do some waiting  ... Is there a gender-neutral pronoun that can replace “his” or “her”? I am using Snow Leopard and Windows 7 with bootcamp. I would like to be able to save some files to my OSX partition from Windows. I would also like to have files (say, photos, source code, etc) that I can manage with both partitions. Is it possible to get the two partitions to "play nice"? Enumerate paragraphs and subparagraphs like sections but with letters I'm using pandoc and in my template.tex exists this code to make the paragraphs and subparagraphs to behave like sections.  % Redefines (sub)paragraphs to behave more like sections \ifx\paragraph\undefined\else \let\oldparagraph\paragraph \renewcommand{\paragraph}[1]{\oldparagraph{#1}\mbox{}} \fi \ifx\subparagraph\undefined\else \let\oldsubparagraph\subparagraph \renewcommand{\subparagraph}[1]{\oldsubparagraph{#1}\mbox{}} \fi   This code generate number like this:  1. chapter  1.1 section  1.1.1 subsection  1.1.1.1 subsubsection  1.1.1.1.1 paragraph  1.1.1.1.1.1 subparagraph   How to change this code to enumerate with letter like this:  1. chapter  1.1 section  1.1.1 subsection  1.1.1.1 subsubsection  1.1.1.1.a paragraph  1.1.1.1.a.a subparagraph Do electrons in an electron beam (cathode ray) follow the ? Or in other words, does the Pauli exclusion principle apply for the beam of electrons? Shared library mappings in /proc/pid/maps Why does /proc/pid/maps contain a few records for the same library ? Here is an example:  7fae7db9f000-7fae7dc8f000 r-xp 00000000 08:05 536861                     /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.20 7fae7dc8f000-7fae7de8f000 ---p 000f0000 08:05 536861                     /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.20 7fae7de8f000-7fae7de97000 r--p 000f0000 08:05 536861                     /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.20 7fae7de97000-7fae7de99000 rw-p 000f8000 08:05 536861                     /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.20   What does this mean ? I am including pages using Ajax but I also need to include their respective javascript files, which requires removing the previous javascript files from memory at the same time.  How can I unload the currently-loaded javascript files (as well as their code in memory) so that I can load the new page's files? They will more than likely conflict, so having multiple independent files' javascript files loaded. Getting arguments underneath \min in an align environment How do I redirect to another webpage? How can I programmatically create a new cron job? I want to be able to programatically add a new cron job, what is the best way to do this?  From , it seems I could dump the current crontab and then append a new one, piping that back into crontab:  (crontab -l ; echo "0 * * * * wget -O - -q http://www.example.com/cron.php") | crontab -   Is there a better way? Every metrizable space with a countable dense subset has a countable basis How to install Redis on Ubuntu 16.04? I am working with Laravel but i have installed all on my own (php, mysql, composer, nginx) and now i need to install Redis and configure it so i could use it for queue driver in Laravel.  How to install it, because it cannot be installed through apt-get install redis  i get this error:  ubuntu@ubuntu:~$ sudo apt-get install redis [sudo] password for ubuntu:  Reading package lists... Done Building dependency tree        Reading state information... Done E: Unable to locate package redis I need to display math in my report, but is it possible to remove the vertical space around align*?  A little example is the following (where I just want the align* to have the same vertical space as a \\  \documentclass[10pt,danish,a4paper,oneside,fleqn]{report}  \usepackage[english]{babel} \usepackage{amsmath}  \begin{document}  ssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssss \begin{align*}   A{\cap}B\ &amp; =\ {\left\{{b,d,e}\right\}}{\;}{\cap}{\;}{\left\{{a,b,f,g}\right\}}   \\   \nonumber\ &amp; =\ {\left\{{b}\right\}} \end{align*} ssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssss \\ ssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssss  \end{document} Simple way to compare processors Today, comparing processors is obviously not just looking at the frequency and the number of cores.  When choosing a new PC, how do you compare processors? Is there some resource, like a site or something that does (not necessarily super-precise) processor comparisons?  Thanks. I remember  due to misuse and I wonder if bots have a part of it. If the bot is POSTing something to my site what are ways I can combat it? I was thinking of setting some cookies and having the cookies changed via JavaScript + timestamp and sign (so yesterday's cookies can't be used today and next week).  I'm sure most people/bots would just use another site instead of enabling JavaScript in their bot.  What else can I do? I'm thinking daily POST limit and a honeypot for generic bots who just randomly post spam. 32-bit vs. 64-bit systems We've had a number of instances over on Stack Overflow involving users who get to the reputation level where they can comment, then spam comments across the site. Due to the lack of community review around comments, these spammed comments can remain on the site for months before someone notices and flags one. Moderators then have to go and manually remove each of these comments. In the last few months, I've personally had to deal with two users who spammed their website across 200+ questions each.  This isn't just limited to people spamming comments with a URL in them. We've had a number of users spray the same nonsense comment or insult across tons of posts and have no one seem to notice for months.  What I'd like is some kind of system-generated notification when a user has posted a barrage of copied-and-pasted comments. This could possibly be triggered when a user has posted a set number of identical comments in a row (4 of them, maybe) or maybe even if they've posted the same comment multiple times. We receive similar system-generated flags when users post duplicate answers, edit many of their posts in a row, or delete many of their own posts at a time.  This system-generated flag should ignore comments generated by review (which have the same text in them). I'm thinking that it shouldn't ignore comments generated by custom off-topic reasons, because someone using the exact same close reason over and over again might be something we want to look into.  The flag itself won't do anything to a user, and would only appear to moderators. I imagine there will be a number of false positives, but it should be easy for us to check these and identify the well-intentioned stock comments from the problematic ones.   We currently have no means of detecting comment spam, so even if this didn't have a great hit rate it would still be beneficial on the balance. Running sample queries for this seems to indicate that it wouldn't have that much noise.  This would allow us to catch comment spam early, and prevent it from living on the site or developing into a more serious problem. Change Recycling Bin Location I have a SSD as a primary hard drive, and one HDD for storage. I want the recycling bin to be on the HDD. I want is so that even if I delete files from the SSD the end up on the HDD's recycling bin. What is the proper way of going about this? Does Devil's Fruit power gained depend on how much of it is eaten? Luffy accidentally ate the Gomu-Gomu (Rubber-Rubber) fruit, but was interrupted by Shanks after a few bites. It was too late and Luffy got the Devil's Fruit powers anyway. If he had instead eaten the whole of it, would he have got even more power from the fruit? Running Synaptic I get the following error message:  E: The package hl1440lpr needs to be reinstalled, but I can't find an archive for it. E: Internal error opening cache (1). Please report.   Upon accepting the message, Synaptic quits.