I want to allow the user to import a module based on their string input argument.  i.e   $python myprogram.py --import_option xyz.py   In python I want something like this after parsing an argument.  arg = 'xyz.py'  import arg #assuming that the module name xyz.py exists.
I'm writing a Python application that takes as a command as an argument, for example:  $ python myapp.py command1   I want the application to be extensible, that is, to be able to add new modules that implement new commands without having to change the main application source. The tree looks something like:  myapp/     __init__.py     commands/         __init__.py         command1.py         command2.py     foo.py     bar.py   So I want the application to find the available command modules at runtime and execute the appropriate one.  Python defines an __import__ function, which takes a string for a module name:     __import__(name, globals=None, locals=None, fromlist=(), level=0)      The function imports the module name, potentially using the given globals and locals to determine how to interpret the name in a package context. The fromlist gives the names of objects or submodules that should be imported from the module given by name.       Source:    So currently I have something like:  command = sys.argv[1] try:     command_module = __import__("myapp.commands.%s" % command, fromlist=["myapp.commands"]) except ImportError:     # Display error message  command_module.run()   This works just fine, I'm just wondering if there is possibly a more idiomatic way to accomplish what we are doing with this code.  Note that I specifically don't want to get in to using eggs or extension points. This is not an open-source project and I don't expect there to be "plugins". The point is to simplify the main application code and remove the need to modify it each time a new command module is added.
How come the PHP private class var is not private? Splitting a large document into several files I am trying to get an intuitive idea of how the  affects Quantum computation. My understanding is that given a qubit $Q$ in superposition $Q_0 \left| 0 \right&gt; + Q_1 \left| 1 \right&gt;$, NCT states another Qubit $S$ cannot be designed such that $S$ is equivalent to the state of $Q$.   Now the catch is, what does Equivalent mean? It could mean either that:   $S = S_0 \left| 0 \right&gt; + S_1 \left| 1 \right&gt;$ such that $S_0 = Q_0, S_1 = Q_1$. Or it could mean that $S = Q$, meaning that if $S$ is observed to be some value ( for example 0) then $Q$ MUST be that same value, and vice versa.    So it seems that point 2, occurs anyways in entangled systems (particularly cat-states), so I can eliminate that option and conclude that that No Cloning states, given a qubit $Q$, it's impossible to make another qubit $S$ such that:  $S = S_0 \left| 0 \right&gt; + S_1 \left| 1 \right&gt;$ such that $S_0 = Q_0, S_1 = Q_1$.  Is this correct? I have a file: Base.h  class Base; class DerivedA : public Base; class DerivedB : public Base;  /*etc...*/   and another file: BaseFactory.h  #include "Base.h"  class BaseFactory { public:   BaseFactory(const string &amp;sClassName){msClassName = sClassName;};    Base * Create()   {     if(msClassName == "DerivedA")     {       return new DerivedA();     }     else if(msClassName == "DerivedB")     {       return new DerivedB();     }     else if(/*etc...*/)     {       /*etc...*/     }   }; private:   string msClassName; };  /*etc.*/   Is there a way to somehow convert this string to an actual type (class), so that BaseFactory wouldn't have to know all the possible Derived classes, and have if() for each one of them? Can I produce a class from this string?   I think this can be done in C# through Reflection. Is there something similar in C++? Infinite sum of ideals I've been trying to prove that given a ring $R$ and a collection of ideals $\{I_{\beta}\}_{\beta \in B}$ in $R$, the set $$\sum_{\beta \in B} I_{\beta}=\{f_1+\cdots+f_r:f_j \in I_{\beta_j}, \mbox{ for some } I_{\beta_j}\}$$ is an ideal and is the smallest ideal containing $\cup_{\beta \in B} I_{\beta}$.  I've already proved when I only have two ideals, and so, using induction, I've seen it for finite sums. But I don't see how to generalise that to an arbitrary family of indexes (maybe infinite) $\beta$.   Could someone please give me a hand? Thank you. Usage of dash (-) in place of a filename For a command, if using - as an argument in place of a file name will mean STDIN or STDOUT.   But in this example, it creates a file with the name -:  echo hello &gt; -   How can I make - in this example mean STDOUT? Conversely, how can I make - mean a file named - in examples such as:  cat - Cross tabulation of two categorical variables: recommended techniques Office 2016 Advanced Setup Powershell Parameters Joined pipelines Considering a routine such as this one:  alpha() { echo a b c |tr ' ' '\n'; }   which outputs a stream, I would like to take the output stream, transform it, and paste it with the original output stream.  If I take use upcasing as a sample transformation, I can achieve what I want with:  $ mkfifo p1 p2 $ alpha | tee p1 &gt;( tr a-z A-Z &gt; p2) &gt;/dev/null &amp; $ paste p1 p2 a       A b       B c       C   My question is, is there a better way to do this, preferably one not involving named pipes? Playing a video in full screen after startup A number of times I have asked a certain kind of ‘attractive nuisance’ question – that is, one in which I anticipate a certain kind of answer would be given that I already know I am going to find insufficient or entirely inadequate. Some examples:      A more abstract example would be asking ‘is it possible to do this 100% correctly’, where people itch to come up with hacks, workarounds and half-baked solutions of various degrees of robustness – while the point of the question is obtaining a fully correct and reliable solution.0 I try to be very explicit in the question body about what kinds of answers I am not interested in. And yet, every time I ask such a question, someone gives such an answer anyway, or an outright XY-type, i.e. frame-challenge answer – where in fact the framing of the question is exactly how I want it, and I don’t want it challenged. Since I have already said in the question body that such an answer would be inaqeduate, when I get one, I downvote it. I believe it’s only appropriate, but it tends not to be received very well – I get insulting comments and downvotes in retaliation. I realise that a proper answer would be much harder to come up with than an ‘obvious’ inadequate answer. I suspect that often a real answer should be negative: ‘there is no way to do that’ or ‘there is no way to answer that for sure’. Nevertheless, if that is the right answer, this is the one I want posted – I don’t want the Internet polluted with more tumbleweed of what is already well-known (and may even be subtly wrong), and I don’t want to give ‘A for effort’ upvotes. What is the most appropriate way to act in such a situation?  0 I am also reminded of when Gary Bernhardt  while trying to avoid reflexive ‘don’t use eval’ replies. Of course, expecting nuance from Twitter of all places is silly, but that’s beside the point. While watching  play for the gold medal in London 2012, I noticed Williams was going about her business while Sharapova was grunting each time she hit the ball.  After doing some , grunting in tennis dates back to 1962. Although men grunt, women draw more attention due to their high-pitched grunts. In addition, there is an initiative to eliminate excess grunts in the next generation of tennis players.  Another quote from said research says:     "I have not found in my 32 years anybody who says grunting or not   grunting has an empirically positive or negative effect on performance   -- it's all about belief system."   What is this "belief system?"  If grunting is not related to performance, why do tennis players do it excessively? How to get a DOM Element from a jQuery selector? single email limit exceeded salesforce very frequently..? my email limit is exceeded after sending 10-12 emails..what could be the problem..as i have seen the limit is 1000 emails/day.i am not able to find out what could be the problem..Can some give me some suggestions. As i also know we can send 10 emails in a single transaction.I am sending emails in a batch class.  I am calling this batch class on button click and filling emailList with emailsId's.                      String query='Select id from Lead';//No use of this query                     Batch_send_emails bse=new Batch_send_emails();                     bse.query=query;                                                         bse.resendEmails=emailList;                     database.executebatch(bse);           **Batch Class**           if(!resendEmails.isEmpty())           {               for(String s:resendEmails)                {                   emailsLeads.add(s);                }           }           Messaging.SingleEmailMessage mail = new Messaging.SingleEmailMessage();         mail.setToAddresses(emailsLeads);        // mail.setCcAddresses(ccAddresses);         String subject='GoToMeeting Invitation Details for '+subject;         String body='test';          mail.setHtmlBody(body);          mail.setSubject(subject);         Messaging.sendEmail(new Messaging.SingleEmailMessage[] { mail });          } I've read before that, by the Principle of Explosion, if a theory is inconsistent, then absolutely any statement can be proven within it.  Obviously, there are statements which are independent of ZFC (Continuum Hypothesis, etc). It seems to me that this proves that ZFC is incomplete. Why does it not then follow that ZFC is consistent? It seems to me that we could say "Assume ZFC is inconsistent. Then the the Continuum Hypothesis is provable in ZFC. But the Continuum Hypothesis is neither provable nor disprovable in ZFC. Therefore ZFC is consistent."  What am I missing here? Atiyah-Macdonald, Exercise 5.4 I was having some trouble with the following exercise from Atiyah-Macdonald.     Let $A$ be a subring of $B$ such that $B$ is integral over $A$. Let $\mathfrak{n}$ be a maximal ideal of $B$ and let $\mathfrak{m}=\mathfrak{n} \cap A$ be the corresponding maximal ideal of $A$. Is $B_{\mathfrak{n}}$ integral over $A_{\mathfrak{m}}$?   The book gives a hint which serves as a counter-example. Consider the subring $k[x^{2}-1]$ of $k[x]$ where $k$ is a field, and let $\mathfrak{n}=(x-1)$. I am trying to show that $1/(x+1)$ could not be integral over $k[x^{2}-1]_{\mathfrak{n}^{c}}$.  I have understood why this situation serves as a counterexample. But I am essentially stuck at trying to draw a contradiction. A hint or any help would be great. Differential Geometry-Wedge product How can we prove the following relation for differentiating the wedge product of a p-form $\alpha_p$ and a q-form $\beta_q$$$d(\alpha_p\wedge\beta _q)=d\alpha_p\wedge\beta_q+(-1)^{p}\alpha_p\wedge d\beta_q$$ Problem printing LaTeX from lua in lualatex I am having difficulty printing LaTeX from a lua function in a LaTeX document processed with lualatex (version 0.70.2). I have a sample that works (if I remove all newlines from the code) and a case that fails. I don't know why these get different results. Here is the sample that fails:  \documentclass{report} \usepackage{luacode} \begin{document}  \begin{luacode*} tex.sprint([[ \begin{tabular}{ | l | l | p{4.in} | }  \hline  {\bf File} &amp; {\bf Cards} &amp; {\bf Summary} \\ \hline  \end{tabular} ]]) \end{luacode*}   \end{document}   I get an error saying:  ! Misplaced \noalign. \hline -&gt;\noalign               {\ifnum 0=`}\fi \hrule \@height \arrayrulewidth \futurelet... l.22 \end{luacode*}   When I put all of the LaTeX code printed from lua on one line the code works fine:  \documentclass{report} \usepackage{luacode} \begin{document}  \begin{luacode*} tex.sprint([[ \begin{tabular}{ | l | l | p{4.in} | } \hline {\bf File} &amp;{\bf Cards} &amp; {\bf Summary} \\ \hline \end{tabular} ]]) \end{luacode*}   \end{document}   So I have a few question.  First, why does the first example shown above fail? It seems like something I am not aware of is being inserted into the generated LaTeX.  Also is there a way for me to see the actual LaTeX that is generated and processed so that I can debug issues like this better?  Is there a way to tell the lualatex to log the actual LaTeX it tries to process?  Any other suggestions for how to debug a problem like this? Why doesn't `sudo cd /var/named` work?