image=[[1,1,1],[1,1,0],[1,0,1]]     visited = [[False] * len(image[0])] * len(image)     visited[0][0] = True print((visited[1][0]))   Shouldn't the above python code print False? Why is the entire column being assigned as True?
I needed to create a list of lists in Python, so I typed the following: my_list = [[1] * 4] * 3  The list looked like this: [[1, 1, 1, 1], [1, 1, 1, 1], [1, 1, 1, 1]]    Then I changed one of the innermost values: my_list[0][0] = 5  Now my list looks like this: [[5, 1, 1, 1], [5, 1, 1, 1], [5, 1, 1, 1]]    which is not what I wanted or expected. Can someone please explain what's going on, and how to get around it?
Derivation of Newton-Euler equations I am in search of a simplified version of the derivation of  (both translational and rotational) for a rigid body (3D block) that has a body fixed frame and where the center of mass of the body is not at the center of gravity.  I can find elementary derivations for the same system when the center of mass is at the center of gravity, but not for my system in question.    I am using the derivation as background research for a rotordynamics project that I'm working on.  Any help and or references would be greatly appreciated!  :) All nilpotent $2 \times 2$ matrices satisfy $A^{2}=0$ Singular or plural "set"? I'm having some issues with a sentence that is part of the purpose in a report that I'm writing. I'm not sure if the word "communicate" (in bold) should be singular or plural.  The applications in the "set" will communicate with each other, not with other "sets".     The purpose of this report is to develop a sample set of applications   that communicates between services on the internet, mobile devices   and a central processing unit in a motor vehicle. So what I decided to do is to start a small case with only 3 people. There are three possible combinations that I could pair up the people, using the symbols A, B, and C to represent the persons involved: A&amp;B, A&amp;C, B&amp;C. The probability of each pair having the same birthday is $1\over365$ (the first guy gets any birthday, and the second guy only gets one birthday to choose from). What my intuition directed me to do next is to find the probability that any of the three events are true, or the union of the three events, which involved adding up the probabilities.   To put this generally, the equation for the probability SHOULD be:  ${n \choose 2} \div 365$  However, clearly this is not the case since $n \choose 2$ gets over 365 when $n = 28$. And with 28 people, there is obviously still a chance that they all have different birthdays (Person 1 has Jan. 1, Person 2 has Jan. 2. ... Person 28 has Jan. 28). Could anyone tell me what's wrong with my intuition? I don't want to know what's the right solution, I just want to know what's wrong with my solution .. it makes sense to my intuition, even though it's incorrect. What's the difference between the following sentences?      (a) I wish they wouldn't make so much noise.   (b) I wish they were not making so much noise.    (c) I wish they did not make so much noise.   I'd appreciate your help. For every vector space $V$ does there exist a linear functional $f$ ( a linear map from $V$ to $F$ the underlying field ) such that for some $ \vec v \in V$ , $f(\vec v) \ne 0$ ? If it does exist , can we prove the existence without the "axiom of choice " ? Is the existence equivalent to axiom of choice ? I know there is a ton of questions and answers about this topic, but none answers my question sufficiently.  Let's say I have a viewport view that I want to render in Cycles. Pressing ALT CTRL Numpad 0 aligns the camera to this view, but it does not solve the whole problem. The thing is, I want PRECISELY this view on the render, preferably in one click, without manually moving the camera back-and-forth, changing sensor sizes etc. fiddling that will remove the unwanted border that appears and blocks the viewport partially. This whole activity wastes a lot of precious time especially if you do this 10 times a day.  What this dream action should do:   match the render resolution (proportions) to the resolution of the current view (can the resolution of current view be read by a Python script?) make the entire view the camera view, without any borders, passe-partout etc. by automatically maneuvering sensor sizes etc. whatever is necessary to make it exactly the same view, the same camera lens angle.   Is it possible to write such a script that would do it all in one click? How to make text aligned left/center/right in the same line? I am trying to align some text to left/center/right in the same line. For example, I want to put my phone number on the left, my name in the center, and my email on the right, how do I do that? $a\equiv\bar a\!\pmod{\!kn}\Rightarrow a\equiv\bar a\!\pmod{\! n};\ $ $(a\bmod kn)\bmod n=a\bmod n.\ $ Congruences persist mod factors of the modulus I noticed relation between modulo operation and number which is power of two  Example I have to calculate $ 3431242341 \mod 2^5 $, which is $ 5 $ but it is equivalent to  $ ( 3431242341 \mod 2^9 ) \mod 2^5 $   I tried many examples and it seems to be true in general, and I am not sure if it is a coincidence or true in general that I can use first modulo operation ( greater number) and the result will be the same. I am having trouble getting onto a server in Minecraft PE on iOS. When I tap on the person's server it just says invalid name:    I have tried turning off and restarting the iPad, going to home screen and logging back into the server but I have had no luck and no change. Is there a reason why this is so? Points at integer distance How many points can one can place in $\mathbb{R}^n$, with the requirement that no $n+1$ points lie in the same $\mathbb{R}^{n-1}$-plane, and the euclidean distance between every two points is an integer? Ubuntu 12.04 gnome issue, no clock is shown, strange starter icon cannot be removed i am finding nowhere a solution I am running UBUNTU 12.04 and using GNOME desktop, which I installed additionally. Logging into classic GNOME I see the following:     WHAT is this "earth globe" icon coming from?Seems to be named "starter". It is configured to open a website, from my bookmarks. WHY is it not showing the TIME?   Using dconf-editor I had no luck in answering the above questions.  Any idea? How many "Recommend Close" votes is too many? Usage and origin of "sister" in expressions like "sister company, sister ship, sister site" etc Many times when going through the Close queue I see that people are using the too localized reason.  Sometimes the reason for this is in the comments (like the syntax error being pointed out), but a lot of times it's in the answer, so then I have to click on the question and look at the answers to see if it is really too localized.  Could we please get the answers shown underneath the question in the Close review queue? Option clash when using graphicx and tikz packages The following code fails Option clash for package graphicx, it seems to be an incompatibility between the package graphicx (when the option pdftex is used) and the package tikz.  \documentclass[a4paper,10pt]{book} \usepackage[T1]{fontenc} \usepackage[utf8x]{inputenc} \usepackage{tikz} \usepackage[pdftex]{graphicx}  \begin{document}      The lazy dog...  \end{document}   I am currently working with Debian wheezy (updated as of 10th November 2012), and the latest TeXLive LaTeX distribution included.  Any ideas? What are these tags related to on the Newest Questions page? On the right, there is a widget that lists "Related Tags" (left − SO April 2013, right − MSE May 2014):         What are they related to? There isn't even a question selected. Are they related to the whole displayed list?  This can be seen on every SE site. Pass a PHP string to a JavaScript variable (and escape newlines) Does adverb placement affect meaning? He swam slowly to the island.  He slowly swam to the island.    Some experts say that there is a “slight difference” in meaning. Would you please tell me that difference? How is arccos derived? Stupid question but I need to understand:  If $ \cos = \dfrac{\text{adjacent}}{\text{hypotenuse}} $  What is arcosine? $ \text{adjacent} \cdot \text{hypotenuse}$? Is this the same for arcsine and arctangent?