Problem with Python
ImportError: No module named pkg_resources
Use "does" in front of another verb in a question? What time does sound good to you?     What time sounds good to you?    Is there a difference? Edit: The previous title didn't really ask the same thing as the question (sorry about that), so I've changed it. To clarify, I understand that the action isn't always a minimum. My questions are in the points 1. and 2. below.  I understand that &quot;principle of least action&quot; is somewhat of a misnomer, since we find that to determine the path taken by a system, we need only impose the condition that the action be stationary, i.e., that $\delta S$ should vanish to first order for small variations of the path, and this leads to the Euler-Lagrange equations. In The Classical Theory of Fields, Landau &amp; Lifshitz discuss the relativistic action for a free particle:  So for a free particle the action must have the form $$S = -\alpha \int_a^b ds$$ (...) It is easy to see that $\alpha$ must be a positive quantity for all particles. In fact, as we saw [earlier], $\int_a^b ds$ has its maximum value along a straight world line; by integrating along a curved world line we can make the integral arbitrarily small. Thus the integral $\int_a^b ds$ with the positive sign cannot have a minimum; with the opposite sign it clearly has a minimum, along the straight world line.  There is also a footnote, addressed a couple of paragraphs earlier, but which is relevant:  Strictly speaking, the principle of least action asserts that the integral $S$ must be a minimum only for infinitesimal lengths of the path of integration. For paths of arbitrary length we can say only that $S$ must be an extremum, not necessarily a minimum.  I have two questions regarding this:  How is the condition &quot;the action must be a minimum for infinitesimal displacements&quot; formulated? I've never heard of that outside of Landau &amp; Lifshitz's books, and in Mechanics they mention it as well but doesn't go into detail. Is this discussed a bit more somewhere?  If for the whole path the action only needs to be stationary, how can we make the argument for the negative sign? If the action had to be a minimum then it would make sense, but surely the fact that $\delta S$ = 0 isn't affected by an overall sign? Find PostgreSQL server hostname on which it runs Create file and its parent directory I know that touch command creates a file:  touch test1.txt   but how I can create a file and its full path?  for example my desktop contains nothing:  ~/Desktop/$ ls ~/Desktop/$   and I want to create 1.txt in ~/Desktop/a/b/c/d/e/f/g/h/1.txt. Can I do this with a simple command like:  $ touch ~/Desktop/a/b/c/d/e/f/g/h/1.txt   instead of create full path manually and then create the file? Optimizing logical sector size for physical sector size 4096 HDD Java Thread priority has no effect GLR Test for 2 samples from exponential distributions Transparent model when exporting fbx file to Unity So I have this shark model which I animated and ready to export it on fbx and transport it to Unity.  But When I put it on Unity, It looks transparent like this.    Many of the solutions online say that the problem is because of my faces, and they told me to recalculate it or something, but normals are just fine. Is there any other solution?  here's the blend file: What tips and advice do you have for photographing the Aurora Borealis? Consider following structure:  . |_s |_s  |_ss  |_ss+   |_sss  |_ss |_s |_s   How can I demote a subsection to subsubsection without changing markups ?  . |_s |_s  |_ss   |_sss+    |_p  |_ss |_s |_s   How can I promote a subsection to section without changing markups ?  . |_s |_s  |_ss |_s+  |_ss  |_ss |_s |_s   A wrapper command would be excellent  \begin[+1]{level} \section{} \end{level} Reconciling different definitions of left-exact functor Suppose that, for a real application, I have ended up with a sorted list A = {$a_1, a_2, ..., a_{|A|}$} of elements of a certain kind (say, Type-A), and another sorted list B = {$b_1, b_2, ..., b_{|B|}$} of elements of a different kind (Type-B), such that Type-A elements are only comparable with Type-A elements, and likewise for Type-B.  At this point I seek to count the following: in how many ways can I merge both lists together, in such a way that the relative ordering of Type-A and Type-B elements, respectively, is preserved? (i.e. that if $P_M(x)$ represents the position of an element of A or B in the merged list, then $P_M(a_i)&lt;P_M(a_j)$ and $P_M(b_i)&lt;P_M(b_j)$ for all $i&lt;j$)  I've tried to figure this out constructively by starting with an empty merged list and inserting elements of A or B one at a time, counting in how many ways each insertion can be done, but since this depends on the placement of previous elements of the same type, I've had little luck so far. I also tried explicitly counting all possibilities for different (small) lengths of A and B, but I've been unable to extract any potential general principle in this way. Eisenstein Criterion with a twist As opposed to the generic polynomial form for utilizing the Eisenstein Criterion ($a_nx^n+a_{n-1}x^{n-1}+\dots+a_0\in\mathbb{Z}[x]$ is irreducible in $\mathbb{Q}$) how do we prove that if $p$ is a prime, $x^{p-1}+x^{p-2}+\dots+x+1$ is irreducible over $\mathbb{Q}$? Since I updated the system to 10.11.5, the Facebook message notification is not showing message text.   Is this a bug in this software upgrade of OSX? Is a hash a zero-knowledge proof? I’m trying to wrap my head around zero knowledge proofs, but I’m having trouble understanding it.  In my current understanding, zero-knowledge proofs prove to the recipient that the sender has a certain knowledge without disclosing it. Like trying to say your password without actually giving it.  Many sources go at it with a convoluted method like a tunnel where there’s a hidden gate, and Bob is trying to know if Alice can go through the hidden gate. But then it starts saying that Bob should not see Alice enter. Wouldn’t it be easier for Bob to just see Alice go in one tunnel and come out the other? That would not disclose the secret way of opening the tunnel, right?  In that line of thinking, given a one-way function like a hash, couldn’t the other person just hash their secret and let the other see that the hashes compare?  I must be missing something (as there’s a lot of research going into it and hashes are well-known), but I can’t wrap my head around it.  Can someone tell me what’s wrong with my understanding of zero knowledge proofs? Allow moderators to fine-tune the effects of a lock Current Situation  When a moderator locks a question or answer, they can choose between different types of post notices: content dispute, off-topic comments, historical significance, wiki answer, or no notice. , but that it works this way is not clear to moderators and it is also not clear what effect a given notice has. The only way to find out for sure is to ask somebody who is not a moderator or use a sock. (This is due to moderator powers possibly overriding the effect of locks.)  Feature Request  Store the effects of a lock separately independent of the post notice. In the interface for locking a post, provide moderators with a checklist regarding the effects of the lock, for example:     This lock prevents:         answers   votes   flags   comments   edits      For questions, also add an option to apply the same lock to all answers to the question. For the canned lock reasons, automatically provide an appropriate choice as defaults.  At the very least make it clear in the dialogue what detailed effects a lock has.  Rationale  Post locks are used rarely, but when they are it is often for important reasons such as avoiding a divide of the community, an escalation of events, or similar. Thus, locks are a tool which moderators have little experience with, but whose correct use (i.e., choosing the right type of effects and knowing what the effects are) may be crucial. Moreover, many locks are used for special cases with individual needs, which in turn require individual locks.  In a specific example, there is a question on Academia, which lead answers and comments, whose appropriateness for the site is subject to a Meta discussion. To avoid further potentially inappropriate comments, answers, etc., I wished to lock question for the remainder of the Meta discussion. I chose content dispute as a lock reason, since it seemed most appropriate notice, however this only prevented edits to the question – which makes sense in other cases but not here. After I noticed this, I chose a historical lock (which I knew to be affecting everything) and removed the post notice (because it was not appropriate). The latter action lead to comments on answers being allowed (), which was not the desired effect either.  Related Questions    – This seems to be partially addressed: The different locks already do have different effects. However, my request goes further than this.  – This is about customising the notice not the effect.  – This would be addressed with this. Proving that an additive function $f$ is continuous if it is continuous at a single point Suppose that $f$ is continuous at $x_0$ and $f$ satisfies $f(x)+f(y)=f(x+y)$. Then how can we prove that $f$ is continuous at $x$ for all $x$? I seems to have problem doing anything with it. Thanks in advance. A customer running Windows 7 Home must have reserved or okayed the Windows 10 upgrade because I am seeing daily messages that the upgrade is failing to install.   This customer is not ready for Windows 10 so it's good that the install is failing. But how to make it stop trying?  Once permission is granted for the upgrade, how do I revoke that permission so it stops attempting to upgrade?  I ran the Windows Update troubleshooter to clear out updates, and I uninstalled and hid KB3035583, but it is still trying to upgrade. In Task Manager, there is no GWX.EXE process.  Event log failure message:  Log Name:      System Source:        Microsoft-Windows-WindowsUpdateClient Date:          8/5/2015 1:28:58 AM Event ID:      20 Task Category: Windows Update Agent Level:         Error Keywords:      Failure,Installation User:          SYSTEM Description:   Installation Failure: Windows failed to install the following update with                 error 0x80240020: Upgrade to Windows 10 Home.   Relevant lines from WindowsUpdate.log:  2015-08-05  01:28:57:885    1068    6698    Agent   ************* 2015-08-05  01:28:57:885    1068    6698    Agent   ** START **  Agent: Installing updates [CallerId = AutomaticUpdates] 2015-08-05  01:28:57:885    1068    6698    Agent   ********* 2015-08-05  01:28:57:885    1068    6698    Agent     * Updates to install = 1 2015-08-05  01:28:57:885    1068    6698    Agent     *   Title = Upgrade to Windows 10 Home 2015-08-05  01:28:57:885    1068    6698    Agent     *   UpdateId = {27E79986-1150-4342-BDD2-76DF82C768D5}.201 2015-08-05  01:28:57:885    1068    6698    Agent     *     Bundles 1 updates: 2015-08-05  01:28:57:885    1068    6698    Agent     *       {FCD6621E-F5D4-4A95-AD43-28F0C58DD2F3}.201 2015-08-05  01:28:58:181    1068    6698    DnldMgr Preparing update for install, updateId = {FCD6621E-F5D4-4A95-AD43-28F0C58DD2F3}.201. 2015-08-05  01:28:58:181    27280   6f84    Misc    ===========  Logging initialized (build: 7.6.7601.18917, tz: -0700)  =========== 2015-08-05  01:28:58:181    27280   6f84    Misc      = Process: C:\Windows\system32\wuauclt.exe 2015-08-05  01:28:58:181    27280   6f84    Misc      = Module: C:\Windows\system32\wuaueng.dll 2015-08-05  01:28:58:181    27280   6f84    Handler ::::::::::::: 2015-08-05  01:28:58:181    27280   6f84    Handler :: START ::  Handler: Windows Setup Install 2015-08-05  01:28:58:181    27280   6f84    Handler ::::::::: 2015-08-05  01:28:58:181    27280   6f84    Handler   : Updates to install = 1 2015-08-05  01:28:58:181    1068    5ecc    AU  &gt;&gt;##  RESUMED  ## AU: Installing update [UpdateId = {27E79986-1150-4342-BDD2-76DF82C768D5}] 2015-08-05  01:28:58:181    1068    5ecc    AU    # WARNING: Install failed, error = 0x80240020 / 0x00000000 2015-08-05  01:28:58:181    27280   6f84    Handler   : WARNING: Exit code = 0x80240020 2015-08-05  01:28:58:181    1068    5ecc    AU  Write OSUpgradeState =14 with OSUpgradephase =2 2015-08-05  01:28:58:181    27280   6f84    Handler ::::::::: 2015-08-05  01:28:58:181    27280   6f84    Handler ::  END  ::  Handler: Windows Setup Install 2015-08-05  01:28:58:181    27280   6f84    Handler ::::::::::::: Under Windows, most applications and application data are stored in a special directory known as C:\Program Files (and occasionally C:\Program Files (x86)). What is the Ubuntu/Linux equivalent to this path? Is there even one? If $\sum (a_n)^2$ converges and $\sum (b_n)^2$ converges, does $\sum (a_n)(b_n)$ converge? If $\sum (a_n)^2$ converges and $\sum (b_n)^2$ converges, does $\sum (a_n)(b_n)$ converge?  Could someone help me to solve this or at least give me a hint?, I have tried using Cauchy's criterion, the Dirichlet test for convergence, etc, but I can´t prove it.Honestly I don´t know where to start. Any help will be appreciated.