Defining attributes of a class in Python
class variable vs instance variable --Python
Why many abstract nouns get an indefinite article while it's taught that abstract nouns shouldn't get it? Boot error > no such device: grub rescue After an installation of Ubuntu 12.04, erasing an old partition with Ubuntu 10.10, I can't get grub to load. I can't access my Windows 7 partition either  I get the message:  &gt; error: no such device: 58ABF29C...   grub rescue&gt;   I suppose my master boot record got erased/corrupted. How can I check and fix this? Permission for snap applications I have some trouble with the Ubuntu notepadqq package. After opening a file from my apache webroot I cannot see any content. Saving the file is also not possible. I thougt this would be a classic permission issue. Therefore, I changed the group of the webroot from root to www-data and added my user to this group. Permissions are 775, so in theory it should now be possible for me to edit files in my webroot. But nevertheless, when I open a file of this directory with notepadqq, it still only shows an empty file.  When using gksudo notepadqq I get the following error message:  No protocol specified QXcbConnection: Could not connect to display :0   I figured out that notepadqq is a so called snap application and I wonder if this is the reason for my problems.  Can someone give me a hint how I could fix this issue (without using 777 permissions)? I know this subject was discussed for many times, but I still don't get it..  I've read in a book that we can use "I've got" instead of "I have" for possesion and it gave some examples,      I've got an English book.   I've got a red car.   So I understand that it can be used only for possession of physical objects, but I saw it used in sentences like "I've got something to say", is it correct? I hope it's not a stupid question..Thank you very much! Generic htaccess redirect www to non-www I would like to redirect www.example.com to example.com. The following htaccess code makes this happen:  RewriteCond %{HTTP_HOST} ^www\.example\.com [NC] RewriteRule ^(.*)$ http://example.com/$1 [L,R=301]   But, is there a way to do this in a generic fashion without hardcoding the domain name? Reading order for Dragonlance? JavaScript property access: dot notation vs. brackets? This question is from [Number Theory George E. Andrews 1-1 #3].     Prove that $$x^n-y^n=(x-y)(x^{n-1}+x^{n-2}y+\ldots+xy^{n-2}+y^{n-1}).$$   This problem is driving me crazy. $$x^n-y^n = (x-y)(x^{n-1}+x^{n-2}y+\dots +xy^{n-2}+y^{n-1)}$$  $(x^n-y^n)/(x-y) =$ the sum for the first $n$ numbers and then I added $(xy^{(n+1)-2}+y^{(n+1)-1})$ which should equal $(x^{n+1}-y^{n+1})/(x-y)$ but I can't figure it out    This is a similar problem in the book and I tried this method but it wasn't working out      $\quad$Thereom $\bf1$-$\bf2$: $\,\,\,\,$ If $\,x$ is any real number other than $1$, then $$\sum_{j=0}^{n-1}x^j=1+x+x^2+\ldots+x^{n-1}=\dfrac{x^n-1}{x-1}.$$    $\quad$Remark: $\displaystyle\sum_{j=0}^{n-1}A_j$ is shorthand for $A_0+A_1+A_2+\ldots+A_{n-1}.$     $\quad$Proof: Again we proceed by mathematical induction. If $n=1$ then $\displaystyle\sum_{j=0}^{1-1}x^j=x^0=1$ and $(x-1)/(x-1)=1$. Thus the theorem is true for $n=1$.  $\quad$ Assuming that $\displaystyle\sum_{j=0}^{k-1}x^j=(x^k-1)/(x-1)$, we find that $$ \eqalign{ \sum^{(k+1)-1}_ {j=0}x^j &amp; = \sum^{k-1}_ {j=0}x^j+x^k=\dfrac{x^k-1}{x-1}+x^k \\ &amp;= \dfrac{x^k-1+x^{k+1}-x^k}{x-1}\\ &amp;= \dfrac{x^{k+1}-1}{x-1}. }$$   Hence condition $(\rm ii)$ is fulfilled, and we have established the theorem.    $\quad$Corollary $\bf1$-$\bf1$: $\,\,$ If $\,m$ and $n$ are positive integers and if $m&gt;1$, then $n&lt;m^n.$ Getting a black screen when installing or Live booting Ubuntu (any version) in my laptop I have an ACER Aspire laptop. Model number is E5-573G-56RG. I bought it only 15 days back. There is no DVD drive in it. I have tried various versions of Ubuntu- 14.04.2, 14.04.3, 15.10, 12.04.5. Tried disabling secure boot, fast startup. I current have Windows 10 Home and Windows 10 PRO (not-activated) installed with GPT partition in UEFI bios. I actually want only the Home edition and Ubuntu 14.04.3 (preferably because of LTS) or 15.10. In case more information is required, kindly ask me..  I tried installing through Wubi, when booting if I choose Ubuntu it automatically restarts and goes into Windows 10 Home! (I didn't have Windows 10 PRO at that time)  NONE OF THE SOLUTIONS I REFERRED HELPED ME.  I have spent 5 days (literally at least 20 hours reading all of them and trying out all kinds of editing in the grub command line, like removing quiet splash, adding and replacing with nomodeset, no splash, acpi_osi=off, acpi_osi=Linux, acpi_backlight=vendor,  acpi_backlight=legacy, noveau.modeset=0, i915.i915_enable_rc6=1 and such things! But I was not able to succeed installing which is why I doubt if there is some more thing to be done or know exactly what has to be done. av_acharya@AnoxBotox:/$ wireshark qt.qpa.plugin: Could not find the Qt platform plugin &quot;xcb&quot; in &quot;path/to/plugins&quot; This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem.   sudo apt-get install --reinstall qt5-default Reading package lists... Done Building dependency tree        Reading state information... Done The following NEW packages will be installed:   qt5-default 0 upgraded, 1 newly installed, 0 to remove and 23 not upgraded. Need to get 0 B/24.4 kB of archives. After this operation, 170 kB of additional disk space will be used. Selecting previously unselected package qt5-default:amd64. (Reading database ... 241279 files and directories currently installed.) Preparing to unpack .../qt5-default_5.12.8+dfsg-0ubuntu1_amd64.deb ... Unpacking qt5-default:amd64 (5.12.8+dfsg-0ubuntu1) ... round() doesn't seem to be rounding properly This is a  about RAID levels.    What are:   the RAID levels typically used (including the RAID-Z family)?  deployments are they commonly found in? benefits and pitfalls of each? What's the quickest Schengen consulate to issue a visa in London? What's the quickest Schengen consulate to issue a Visa in London? Basically I want to travel as fast as possible to France, and since any Schengen visa will work, I want to go to the consulate with the shortest processing time. Show that if $a \equiv b \pmod n$, $\gcd(a,n)=\gcd(b,n)$ Quick way to remove solidify thickness I have made the mesh and added solidify modifier and applied. But later i thought to increase the thickness. So now i want to remove thickness so that i can added the solidify modifier again. I want to know is there any quick remove thicknes. When i select the edge then ctrl+ the selection goes downward not to single face. So i want to know a quick way to decrease thickness. Any suggestion or help. Are there any examples of subspaces  of $\ell^{2}$ and $\ell^{\infty}$ which are not closed? Recently, Firefox has changed the default folder for newly created bookmarks (using Ctrl+D) from the Bookmarks Menu to "Other Bookmarks".  Is there some way to change that back? Or some alternate method instead of Ctrl+D?  EDIT  A native way to do this (without an add-on) would be best. Is there an example of a ring $S$ with identity $1_S$ containing a non-trivial subring $R$ which itself has an identity $1_R$, but $1_R\neq 1_S$ (or equivalently $1_S\notin R$). I'd also like to know under what conditions the identities have to be equal. I know they must be equal if $S$ has no zero divisors, since for every $r\in R$ we have $(1_S-1_R)r=0$  In other words: Is the category of unital rings with identity-preserving morphisms a full subcategory of the category of rings (where morphism are only required to respect addition and multiplication)? Prove that polynomial of degree $4$ with real roots cannot have $\pm 1$ as coefficients (IITJEE) So I was going through  my 11th class package on Quadratic equations and I saw a question to prove that a polynomial of $4$th degree with all real roots cannot have $\pm 1$ as all its coefficients.   I tried proving it using calculus, by showing that at least one consecutive maxima  and minima will lie either above or below the x axis, but couldn't solve it using that.  I also tried using Descartes Rule of Signs but couldn't solve it with that too. Any help? Java. Splitting a multiple word string into two word strings every space