Unexpected problem with a simple code that creates nested lists I wrote a really simple code to create some nested lists, and I got an unexpected problem, that while loop doesn't end.  Have no idea what is wrong in it. If you have any clues, would much appreciate it)  import random  square = [0,0,0,0,0,0,0,0,0] squares = []  def allsquares():     for i in range(9):         squares.append(square)     return squares   def autofill():         for i in range(9):             fn = random.randint(1,3)             sn = random.randint(6,8)             for s in range(fn,sn):                 print('Mary Sue')                 d = True                 while d:                     x = random.randint(0,8)                     print(x)                     if squares[i][x] == 0:                         d = False                 squares[i][x] = random.randint(1,9)         return squares    allsquares() autofill() print(squares[2])
List of lists changes reflected across sublists unexpectedly 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?
Prove $[\sin x]' = \cos x$ without using $\lim\limits_{x\to 0}\frac{\sin x}{x} = 1$ I came across this question:   From the comments, Joren said:     L'Hopital Rule is easiest: $\displaystyle\lim_{x\to 0}\sin x = 0$ and $\displaystyle\lim_{x\to 0} = 0$, so $\displaystyle\lim_{x\to 0}\frac{\sin x}{x} = \lim_{x\to 0}\frac{\cos x}{1} = 1$.   Which Ilya readly answered:     I'm extremely curious how will you prove then that $[\sin x]' = \cos x$   My question:  is there a way of proving that $[\sin x]' = \cos x$ without using the limit $\displaystyle\lim_{x\to 0}\frac{\sin x}{x} = 1$. Also, without using anything else $E$ such that, the proof of $E$ uses the limit or $[\sin x]' = \cos x$.    All I want is to be able to use L'Hopital in $\displaystyle\lim_{x\to 0}\frac{\sin x}{x}$. And for this, $[\sin x]'$ has to be evaluated first.    Alright... the definition that some requested.   Def of sine and cosine: Have a unit circumference in the center of cartesian coordinates. Take a dot that belongs to the circumference. Your dot is $(x, y)$. It relates to the angle this way: $(\cos\theta, \sin\theta)$, such that if $\theta = 0$ then your dot is $(1, 0)$.  Basically, its a geometrical one. Feel free to use trigonometric identities as you want. They are all provable from geometry. How to find real world Selenium projects Where can I find sample or real Selenium projects. All the material I can find on github and on internet are basic, and never intermediate or advanced.  How does a real Selenium project look in real life? How can I find sample code? Why does my wife's skin buzz when she's using her laptop? When my wife uses her laptop, if I touch her skin, I can feel a buzz.  She doesn't feel the buzz, but she can hear it if I touch her ear.  So I'm guessing it's a faulty laptop, and she's conducting an electrical current.  But why would she not feel anything, and what would it be that she would be hearing when I touch her ear?    More info:  The effect is only intermitent - it's pretty reliable in a single session on the laptop, but some sessions it won't happen and others it will.  I had the same sensation with a desk lamp that I had several years ago, with no moving parts (as far as I could tell)  The effect only occurs when I move my finger - if I'm stationary, I don't notice anything.   I was playing with my son, and noticed the same buzz.  First I thought he was touching the laptop.  Then I realised he had skin-to-skin contact with my wife who was using the laptop. Must one have a knowledge of fine art to be a Graphic Designer? Should all Graphic Designers know how to draw? The Sitemap Paradox We use a  on Stack Overflow, but I have mixed feelings about it.  Web crawlers usually discover pages from links within the site and from other sites. Sitemaps supplement this data to allow crawlers that support Sitemaps to pick up all URLs in the Sitemap and learn about those URLs using the associated metadata. Using the Sitemap  does not guarantee that web pages are included in search engines, but provides hints for web crawlers to do a better job of crawling your site.  Based on our two years' experience with sitemaps, there's something fundamentally paradoxical about the sitemap:  Sitemaps are intended for sites that are hard to crawl properly. If Google can't successfully crawl your site to find a link, but is able to find it in the sitemap it gives the sitemap link no weight and will not index it!  That's the sitemap paradox -- if your site isn't being properly crawled (for whatever reason), using a sitemap will not help you! Google goes out of their way to make :  &quot;We cannot make any predictions or guarantees about when or if your URLs will be crawled or added to our index&quot;  &quot;We don't guarantee that we'll crawl or index all of your URLs. For example, we won't crawl or index image URLs contained in your Sitemap.&quot;  &quot;submitting a Sitemap doesn't guarantee that all pages of your site will be crawled or included in our search results&quot;   Given that links found in sitemaps are merely recommendations, whereas links found on your own website proper are considered canonical ... it seems the only logical thing to do is avoid having a sitemap and make damn sure that Google and any other search engine can properly spider your site using the plain old standard web pages everyone else sees. By the time you have done that, and are getting spidered nice and thoroughly so Google can see that your own site links to these pages, and would be willing to crawl the links -- uh, why do we need a sitemap, again? The sitemap can be actively harmful, because it distracts you from ensuring that search engine spiders are able to successfully crawl your whole site. &quot;Oh, it doesn't matter if the crawler can see it, we'll just slap those links in the sitemap!&quot; Reality is quite the opposite in our experience. That seems more than a little ironic considering sitemaps were intended for sites that have a very deep collection of links or complex UI that may be hard to spider. In our experience, the sitemap does not help, because if Google can't find the link on your site proper, it won't index it from the sitemap anyway. We've seen this proven time and time again with Stack Overflow questions. Am I wrong? Do sitemaps make sense, and we're somehow just using them incorrectly? I would like to open 4 Notepad++ windows at once, in the same pannel. Currently, I am only able to split it into two, and would like to know if there is a plugin that enables 4 views at at same time, or 3.   thanks Two footnotes in a heading, only one is displayed at the end of the page I'm adding two footnotes to a section heading:  \documentclass{article} \usepackage[english]{babel} \usepackage[utf8]{inputenc} \usepackage[T1]{fontenc} \usepackage{lipsum}  \usepackage[stable]{footmisc}  \usepackage{titlesec}  \begin{document} \section{test \footnote{This is footnote no1.} \footnote{This is footnote no2.} } \lipsum[4] \end{document}   The heading will have both of the footnotes, but at the end of the page only the second is displayed. The problem appears to be \usepackage{titlesec}, because it works fine without it.    Stuff I specified in \usepackage{titlesec}:  \renewcommand\thesection{\arabic{section}}  \renewcommand\thesubsection{\arabic{subsection}}  \renewcommand\thesubsubsection{\arabic{subsubsection}}  \titleformat{\section}[block]{\Large\scshape\centering}{\thesection}{1em}{}  \titleformat{\subsection}[block]{\large\scshape}{\thesection.\thesubsection}{1em}{}  \titleformat{\subsubsection}[block]{\large\scshape}{\thesection.\thesubsection.\thesubsubsection}{1em}{}   Thanks in advance! Can I programmatically open the devtools from a Google Chrome extension? Enable 'on the fly' CRS transformation in QGIS 3? Piping data through arbitrary functions in Clojure My created page with link  The 404 page after following my new url. Is there any difference between "offense" and "offence"? Feeling a tingling sensation by touching stuff, Is this safe? I'm putting on my desktop computer on steel rack as usual. A while ago, when I touch the steel rack for seconds, practically I feel a tingling sensation, sort of electrical shock in my finders. After that I measured how voltage the steel rack has, the multi-tester meter indicated almost 50V by AC mode. Is this safe to touch or keep the PC on the position, or I should get away the PC somewhere electricity-safe? I'm not sure this site is suit for asking this kind of question, but I'm very worrying whether this is safe or not since this experience is my very first time. Thank you. Merging two incoming broadband lines for faster Internet Add an Image Upload button to the Mobile Site With the release of iOS 6, the most commonly used mobile browser now supports standard generic image upload buttons. This is actually really handy.  I can take screenshots on my phone or iPad, and use them to answer questions about apps made to run on those devices (or ) to answer questions. Until the release of iOS 6 however, the only way to use these images in my answer was to either sync them over to my computer, and then answer from a desktop, or use a specialized app to upload the images, such as PicUp or DropBox, and then manually write out the markdown code.  After iOS 6, the Image Upload button works just fine, if I switch to viewing the full site from my iDevice, rather than the mobile view. I can upload images directly, and the markdown is handled for me. It's awesome, except for the fact that the non-mobile site is decidedly non-awesome on the small screen of my phone.  Which brings me to my feature request: Add the Image Upload button (and other markdown shortcuts, as deemed worthwhile) to the ask/answer editors on the mobile version of SE sites. Are there any differences between Skyrim & Skyrim: Special Edition? I am aware of the basics of evolutionary theory, however I don't understand how mutations can add genes over time.   Am I correct in thinking that creatures within the same species who mutate to have an additional gene in their genome would normally be infertile?  Or am I misunderstanding that?  Can someone explain the process of the creation of genetic material through evolution?  Citation to a decent academic paper or book on the matter would be appreciated too. Suppose that $y_1(x)$ and $y_2(x)$ are solutions of the differential equation $y''+py'+qy=0$ on $I$. How can I show that if $y_1$ and $y_2$ vanish at the same point then they are not linearly independent?   Here is my attempt to prove the problem. Since $y_1(x)$ and $y_2(x)$ are solutions of the differential equation $y''+py'+qy=0$ on $I$, it is enough for me to show that the Wronskian of $y_1$ and $y_2$ denoted by $W(y_1,y_2)$ is zero. Now since $y_1$ and $y_2$ vanish at the same point say $p$ we have $y_1(p)=0$ and also $y_2(p)=0$.   Solving for $W(y_1,y_2)(p)$ we have: $y_1(p)y_2'(p)-y_2(p)y_1'(p)=0$ since $y_1(p)=0$ and also $y_2(p)=0$.   Am I correct? Thanks Reduce Spacing In $$ In math, one often needs to put a letter inside the symbols &lt;&gt;, e.g. to denote a cyclic group &lt;x&gt; generated by some element x. However, plain text displays the symbols &lt; and &gt; as an upside down exclamation point and an upside down question mark, respectively, while math type displays a large space like so:  &lt; x &gt;    Is there some way to reduce this spacing? If $G$ is a group, show that $x^2ax=a^{-1}$ has a solution if and only if $a$ is a cube in $G$