When I try to add or multiply in a python3, I get an obvious error, although the operation is very simple and can be easily verified.  # for example:  a = 0.3 * 3 b = 0.3 + 0.3 + 0.3 c = 0.6 + 0.3  print('a = ',a) print('b = ', b) print('c = ',c)   I expect the answer to be 0.9, but it is different.  a =  0.8999999999999999 b =  0.8999999999999999 c =  0.8999999999999999   Can someone explain why this is happening. I use: Python 3.6.8 :: Anaconda custom (64-bit)
Consider the following code:   0.1 + 0.2 == 0.3  -&gt;  false   0.1 + 0.2         -&gt;  0.30000000000000004   Why do these inaccuracies happen?
Preventing itemize environment to insert initial vertical space Why were the villagers and the axe-wielding hitman brothers crawling towards a shrine? At the start of Season 3 Breaking Bad, we see a bunch of villagers and Tuco's cousins crawling on their bellies towards some shrine where they put a drawing of Walter White as some kind of "offering".  Why were the villagers and the cousins crawling towards this shrine? Finding functions such that $f(g(x)) = f(x)g(x)$ Let's assume the functions in question are continuously differentiable. If $f(g(x)) = f(x)g(x)$, then: $$f'(g(x))g'(x) = f'(x)g(x)+f(x)g'(x)$$ I attempted to find a particular solution by letting $g(x) = x$. Then, $$f'(x) = xf'(x) + f(x)$$ $$df = xdf + fdx$$ $$\frac{df}{f} = \frac{dx}{1-x}$$ $$\ln(f(x)) = -\ln(1-x)+C$$ $$f(x) = \frac {A}{1-x}$$ Where $A$ is a constant. This solution was fairly unsatisfying to me, and upon checking it, I see it doesn't actually work, as letting $g(x) = x$ leads to $f(x) = xf(x)$. I was wondering if there were better answers, or at least a less trivial way to go about the problem. How do I break out of a loop in Perl? I'm trying to use a break statement in a for loop, but since I'm also using strict subs in my Perl code, I'm getting an error saying:     Bareword "break" not allowed while   "strict subs" in use at ./final.pl   line 154.   Is there a workaround for this (besides disabling strict subs)?  My code is formatted as follows:  for my $entry (@array){     if ($string eq "text"){          break;     } } How are parameters evaluated for a Plot in Manipulate Can infinitely many primes lie over a prime? Why do my LED lights stay on, even when the switch is off? When is the union of a family of subspaces of a vector space also a subspace? It is not difficult to prove that the union of a chain (or, more generally, a directed family) of subspaces of a vector space $V$ is a subspace of $V$.   Given a family $\mathcal{F}$ of subspaces of a vector space $V$ such that the union of $\mathcal{F}$ is a subspace of $V$, is it true that $\mathcal{F}$ is a directed family?  If not, is there a "nice" characterization of families of subspaces whose union is a subspace? How to connect and disconnect to a network manually in terminal? Since the network manager is troubling me so much I want to replace it (possibly wicd orNM from ppa:volanin).  I do not know how to connect and disconnect to the network through the terminal without using network manager.  I would like a command-line way of managing the network. Why do we use Hermitian operators in QM? Position, momentum, energy and other observables yield real-valued measurements. The Hilbert-space formalism accounts for this physical fact by associating observables with Hermitian ('self-adjoint') operators. The eigenvalues of the operator are the allowed values of the observable. Since Hermitian operators have a real spectrum, all is well.  However, there are non-Hermitian operators with real eigenvalues, too. Consider the real triangular matrix:  $$ \left( \begin{array}{ccc} 1 &amp; 0 &amp; 0 \\ 8 &amp; 4 &amp; 0 \\ 5 &amp; 9 &amp; 3 \end{array} \right)  $$  Obviously this matrix isn't Hermitian, but it does have real eigenvalues, as can be easily verified.  Why can't this matrix represent an observable in QM? What other properties do Hermitian matrices have, which (for example) triangular matrices lack, that makes them desirable for this purpose? How can I add four spaces before each lines of programs code in terminal How to use CDF and PDF statistics for analysis This may be too much of a general question but I hope I can find help here. I am starting a RA job in my university and my topic will be related to Internet Traffic Analysis. I am fairly new to the world of analysis but I guess in the world of research this is what I have to do a lot of.  I've been through a few papers and in a lot of them I find they use Probability Density (PDF), CDF, CCDF etc to explain the results they've obtained. For example, PDF of user session duration, CDF of bytes transferred each day etc. I have taken probability and statistics class so I understand what they are but I am still confused to the cases in which such representation would be chosen.  So, if there is anyone out there who does such graphs and analysis (in any other topic in general or this) could you tell me simply in what situation would I use one or the other of these representations This question exists as it fills a specific criterion.  While you are encouraged to help maintain its answers, please understand that "big list" questions are not generally allowed on Ask Ubuntu and will likely be closed per the . More information on the .   What kind of desktop environments or shells are there for Ubuntu users to install?  Please list a desktop environment or shell for each:   a description on why you like or suggest it (features, performance, etc.). a good screenshot, preferably of it running on Ubuntu and showing off some of its features. the minimal requirement for it to be usable, If there's any setting to lower it's requirement (Like kde's low-fat profile); how to enable the said setting some instructions on how to set it up if in the repositories, please provide a software centre link I am trying to create a map in both Leaflet and OpenLayers 3 which displays the  layer EMAP8 from the WMS http://wms.nlsc.gov.tw/wms. I can't get it to work. I can open the layer in QGIS, but when I try to use it in Leaflet like this:  var overlay_taiwanemapen0 = L.tileLayer.wms('http://wms.nlsc.gov.tw/wms', {     layers: 'EMAP8',     format: 'image/png',     transparent: true,     continuousWorld : true, });   or in OpenLayers 3 like this:  var lyr_taiwanemapen = new ol.layer.Tile({     source: new ol.source.TileWMS(({         url: "http://wms.nlsc.gov.tw/wms",         params: {"LAYERS": "EMAP8", "TILED": "true"},     })),     title: "taiwane-map(en)", });   I get nothing displayed. I can see layers being requested, and data being transferred, but nothing on the map.  What am I doing wrong? Ubuntu 17.10 and later: can't change the input switching shortcut to alt+shift When I try to set the default combo for switching to different language layouts in my keyboard from Shift+Super+Space to Alt+Shift I can't.  I used to have this combo since Ubuntu 14 and even before that when I used to have Windows. Now for some stupid reason it does not allow (actually nothing happens its not like I get an error or the combo is used elsewhere). How could I bypass this bug? Why do I need multiple sites for the same property in Google Webmaster Tools? In researching the best practice for adding sites to the Search Console, I've often seen it suggested to add separate properties for different versions of the same website. Even in  it states:     "Similarly, if your site has http:// and https:// versions, you should   add each as a separate site."   I've seen the same suggested for www/non-www. So if a site is accessible at all the variations of http/s and www/non-www we should have four properties.  But what if the site is only accessible at one variant? i.e. https and www are forced via htaccess, so only  can ever be accessed - should we still add all the variants?   In essence, the problem is that I don't know why Google wants us to do this, so I can't work out if it'll be ok just to have one instance. After these instructions in the Python interpreter one gets a window with a plot:  from matplotlib.pyplot import * plot([1,2,3]) show() # other code   Unfortunately, I don't know how to continue to interactively explore the figure created by show() while the program does further calculations.  Is it possible at all? Sometimes calculations are long and it would help if they would proceed during examination of intermediate results. I'm new to regular expressions and would appreciate your help.  I'm trying to put together an expression that will split the example string using all spaces that are not surrounded by single or double quotes. My last attempt looks like this: (?!") and isn't quite working. It's splitting on the space before the quote.  Example input:   This is a string that "will be" highlighted when your 'regular expression' matches something.   Desired output:  This is a string that will be highlighted when your regular expression matches something.   Note that "will be" and 'regular expression' retain the space between the words. Omission of the indefinite article to eliminate ambiguity love between husband and wife   What is the reason that there is no article (e.g. "love between a husband and a wife") in the above? Has some kind of a rule been identified grammatically when it comes to such a case? If I were to guess I think it's because the indefinite article 'a', the purpose of that, is taking a generic sample (or 'instance') from a 'class' (the class of husbands), but in the above sentence you want to refer to the class itself... the husband class and the wife class... and not an 'instance' of them, because it just is more to the point. Do you think this is a fair reasoning? Also, a thought came to me that with the use of the indefinite article, you get a generic husband and a generic wife, which, may not necessarily love each other (for they are not a specific pair of a specific husband and a specific wife who in fact love each other). Is it a bad practice to catch Throwable?