I am a python newbie and I keep seeing code like:  import numpy as np rng = np.random.RandomState(4)  # generate some random data to train on get_rand = lambda *shape: np.asarray(rng.rand(*shape) &gt; 0.5, dtype='float32')   Is * referring a pointer ? Please help me in understanding what does * do here (I know C so I guess this looks like a pointer, but it can't be).
In the following method definitions, what does the * and ** do for param2?  def foo(param1, *param2): def bar(param1, **param2):
How to insert spaces up to column X to line up things in columns? Moving from HTTP to HTTPS in Google Search Console Importance of Representation Theory Representation theory is a subject I want to like (it can be fun finding the representations of a group), but it's hard for me to see it as a subject that arises naturally or why it is important. I can think of two mathematical reasons for studying it:   The character table of a group is packs a lot of information about the group and is concise. It is practically/computationally nice to have explicit matrices that model a group.   But there must certainly be deeper things that I am missing. I can understand why one would want to study group actions (the axioms for a group beg you to think of elements as operators), but why look at group actions on vector spaces? Is it because linear algebra is so easy/well-known (when compared to just modules, say)?  I am also told that representation theory is important in quantum mechanics. For example, physics should be $\mathrm{SO}(3)$ invariant and when we represent this on a Hilbert space of wave-functions, we are led to information about angular momentum. But this seems to only trivially invoke representation theory since we already start with a subgroup of $\mathrm{GL}(n)$ and then extend it to act on wave functions by $\psi(x,t) \mapsto \psi(Ax,t)$ for $A$ in $\mathrm{SO}(n)$.   claims that if our physical system has $G$ as a symmetry group, then there is a correspondence between particles and representations of $G$. I'm not sure if I understand this correspondence since it seems to be saying that if we act an element of G on a state that corresponds to some particle, then this new state also corresponds to the same particle. So a particle is an orbit of the $G$ action? Anyone know of good sources that talk about this? Have men and women in the Wizarding World always had relatively equal rights? There are racial struggles and examples of racism, (Muggle-borns, centaurs, hous-elves, goblins, etc.) but are there any examples in the Wizarding World of sexism?  Have witches and wizards always had equal rights? Prove $(a^2+b^2)(c^2+d^2)\ge (ac+bd)^2$ for all $a,b,c,d\in\mathbb{R}$. Prove $(a^2+b^2)(c^2+d^2)\ge (ac+bd)^2$ for all $a,b,c,d\in\mathbb{R}$.  So $(a^2+b^2)(c^2+d^2) = a^2c^2+a^2d^2+b^2c^2+b^2d^2$  and $(ac+bd)^2 = a^2c^2+2acbd+b^2d^2$  So the problem is reduced to proving that $a^2d^2+b^2c^2\ge2acbd$ but I am not sure how to show that When a land becomes creature, can you kill it? How do I specify a pointer to an overloaded function? Massive 404 attack with non existent URLs. How to prevent this? The problem is a whole load of 404 errors, as reported by Google Webmaster Tools, with pages and queries that have never been there. One of them is viewtopic.php, and I've also noticed a scary number of attempts to check if the site is a WordPress site (wp_admin) and for the cPanel login. I block TRACE already, and the server is equipped with some defense against scanning/hacking. However, this doesn't seem to stop. The referrer is, according to Google Webmaster, totally.me.  I have looked for a solution to stop this, because it isn't certainly good for the poor real actual users, let alone the SEO concerns.  I am using the Perishable Press mini black list (), a standard referrer blocker (for porn, herbal, casino sites), and even some software to protect the site (XSS blocking, SQL injection, etc). The server is using other measures as well, so one would assume that the site is safe (hopefully), but it isn't ending.  Does anybody else have the same problem, or am I the only one seeing this? Is it what I think, i.e., some sort of attack? Is there a way to fix it, or better, prevent this useless resource waste?  EDIT I've never used the question to thank for the answers, and hope this can be done. Thank you all for your insightful replies, which helped me to find my way out of this. I have followed everyone's suggestions and implemented the following:   a honeypot a script that listens to suspect urls in the 404 page and sends me an email with user agent/ip, while returning a standard 404 header a script that rewards legitimate users, in the same 404 custom page,  in case they end up clicking on one of those urls. In less than 24 hours I have been able to isolate some suspect IPs, all listed in Spamhaus. All the IPs logged so far belong to spam VPS hosting companies.   Thank you all again, I would have accepted all answers if I could. After Upgrade to Ubuntu 20.04: "Oh no! Something went wrong" Could there be a bit of reputation leakage between the sites, please? Expected number of hamiltonian paths in a tournament The following theorem is from Alon&amp;Spencer's The probabilistic method, in the beginning of chapter 2:  Theorem 2.1.1: There is a tournament $T$ with $n$ vertices and at least $\frac{n!}{2^{n-1}}$ Hamiltonian paths.  Briefly the theorem is proved by looking at $X_\sigma$ the indicator random variable for a permutation $\sigma$ giving a Hamiltonian path, that is, satisfying $(\sigma(i),\sigma(i+1))\in T$ for $1\leq i \lt n$. Then   $\sum \mathbb{E}\left[X_\sigma\right] = \frac{n!}{2^{n-1}}$.  I don't understand where did this value ($\frac{n!}{2^{n-1}}$) came from! could someone explain it please? Implementing switch cases I'd like to have command built around a switch-case environment in LaTeX, much like the example below:  \documentclass{article}  \usepackage{xstring}  \newcommand{\dothis}[1]{% \IfStrEqCase{#1}{{a}{so you typed a}     {b}{now this is b}     {c}{you want me to do c?}}     [nada] }  \begin{document}  \dothis{a}  \dothis{b}  \dothis{c}  \dothis{e}  \end{document}   My problem with it is that it requires the xstring package. Is there any other way to do this? Preferably without loading additional packages and avoiding disgraceful thickets of \if-\else-\fi statements? How to factor a fourth degree polynomial I'm working on a math problem but I am having a hard time figuring out the method used by my textbook to make this factorization:  $$x^4 + 10x^3 + 39x^2 + 70x + 50 = (x^2 + 4x + 5)(x^2 + 6x + 10)$$  I've tried to see if this equation can be factored by grouping or by long division to no avail. Any help would be greatly appreciated. Is $\sin \infty$ an indeterminate form? I had a  over what seems like a simple question:     Is $\sin \infty$ an ?   What do you think? :)    I'm labelling this as (soft-question) to be safe, but it should have a clear answer depending on the definition of indeterminate form used. The term "indeterminate form" is seldom used in post-calculus mathematics, but I believe it has one or more accepted definitions, which are either informal or formal. So any answer which takes a standard definition and argues the case would be interesting to me.  How to make a good answer:   State the definition of indeterminate form, either from an online or textbook source, or a definition you came up with on your own. Determine, using your stated definition, whether $\sin \infty$ is indeterminate or not.   EDIT: What do I mean by $\sin (\infty)$?  It's not a well-defined expression, but neither are any of the other indeterminate forms: $\frac{0}{0}$ doesn't exist, $1^\infty$, doesn't exist, and so on. So the question is whether this expression -- which is not well-defined, just like any other indeterminate form -- is an indeterminate form. Why would perfectly similar data have 0 mutual information? Converting points to raster in ArcGIS? Leaving Italy without paying a bus fine My wife and I got bus fines today in Bologna. We had only recently arrived and had purchased a ticket from where we were staying which was about 6 or 7 km from the city. The hotel receptionist explained the ticketing system to us and said that if we buy a ticket we could use it on as many journeys for 75 minutes.  We took the bus from our hotel to Bologna and then straight away got on another bus to get to central Bologna where all the sights are. When we got on this other bus we assumed that it was ok as we were still within the 75 minutes. However, when we tried to validate our tickets in the machine it flashed red like an error had occurred so we figured something wasn't right.   We tried to ask the driver about it or if we could buy a ticket but he just grunted and started to drive off. We therefore started to leave the bus at the next stop so we could try and buy another ticket but were ushered back on by a few men who turned out to be ticket inspectors!  They alleged that our tickets were not valid in the city and that we had to pay a 65 euro fine. They wanted to see our official documentation and so took details from our UK driving licences and issued us both with fines. They wanted us to pay there and then, but we explained we didn't have enough cash on us to do so and they then stated we could pay by card.   However, I still wasn't happy about doing that so he then said that we could pay later by going to an Italian post office; or if we don't pay within a certain time the fine will go up to 270 euros each and will be posted to us (he got our addresses off our UK driving licences)!  I am a bit miffed about this as we were noway trying to evade and as soon as we realised our mistake we tried to talk to the bus driver to buy a ticket or get off the bus, but he drove off and ignored us! I have a slight suspicion that it was a rouse as it is very strange that he did this and then out of nowhere bus inspectors got on and made a beeline for us!  If we go back to the UK without paying these fines and ignore the subsequent fines that they send us through the post (if they do send any), then what happens? Do they have any powers when we are back in the UK? a total fine of 500 euros for an honest mistake seems utterly outrageous.   Fine below How can we run a command stored in a variable? $ ls -l /tmp/test/my\ dir/ total 0   I was wondering why the following ways to run the above command fail or succeed?  $ abc='ls -l "/tmp/test/my dir"'  $ $abc ls: cannot access '"/tmp/test/my': No such file or directory ls: cannot access 'dir"': No such file or directory  $ "$abc" bash: ls -l "/tmp/test/my dir": No such file or directory  $ bash -c $abc 'my dir'  $ bash -c "$abc" total 0  $ eval $abc total 0  $ eval "$abc" total 0 Two possessive nouns in a row Is this the proper way to use two possessive nouns in a row?     I am going over to Lauren's parents' house this evening.   or     The store's manager's niece was quite attractive.   What about three?*     The United States Army's general's wife's dog is on the lamb, somebody stop it.   *Three seems both unrealistic, and in the specific example I used you could make a case for adding a fourth United State's Army's but I think that seems even more unrealistic.  Additionally, I would never write this in any sort of setting other than the purpose of knowing what the rules are.  Thanks in advance, I apologize in advance if this is duplicate My Ubuntu laptop which was working fine until recently. My desktop disappeared and all the desktop icons are gone. All I have access to is the terminal. In an attempt to fix the problem, I installed GNOME but it made the computer give the error:     Warning! Failed to connect to lvmetad. No such file or directory Falling back to internal scanning.    I can press Ctrl+Alt+F1 to start tty1 but I can't get to a graphical user interface. What did I do wrong and how do I fix it?.  The operating system is ubuntu Linux