The opposite of list flattening.  Given a list and a length n return a list of sub lists of length n.  def sublist(lst, n):     sub=[] ; result=[]     for i in lst:         sub+=[i]         if len(sub)==n: result+=[sub] ; sub=[]     if sub: result+=[sub]     return result   An example:  If the list is:  [1,2,3,4,5,6,7,8]   And n is:  3   Return:  [[1, 2, 3], [4, 5, 6], [7, 8]]   Is there a more eloquent / concise way?  An aside, what is preferred when appending lists to lists (in the context above):  list1+=[list2]   Or:  list1.append(list2)   Given that (according to Summerfeild's 'Programming in Python 3') they are the same?  Thanks.
I have a list of arbitrary length, and I need to split it up into equal size chunks and operate on it. There are some obvious ways to do this, like keeping a counter and two lists, and when the second list fills up, add it to the first list and empty the second list for the next round of data, but this is potentially extremely expensive.  I was wondering if anyone had a good solution to this for lists of any length, e.g. using generators.  I was looking for something useful in itertools but I couldn't find anything obviously useful. Might've missed it, though.  Related question:
example of compact operator Let $E=l^p=\left\{x=\left(x_n\right): x_n\in\mathbb{R}, \sum_{1}^{\infty}\left|x_n\right|^p&lt;\infty\right\}$ with $1\le p&lt;\infty$, $\left\|x\right\|_E=\left(\sum_{1}^{\infty}\left|x_n\right|^p\right)^{1/p}.$ Let $\left(\lambda_n\right)$ is a bounded sequence in $\mathbb{R}$ and consider the operator $T$ defined by $$T(x)=\left(\lambda_1x_x,\ldots,\lambda_nx_n,\ldots\right)$$ where $x\in l^p$. Prove that $T$ is a compact operator from $E$ to $E$ iff $\lambda_n\rightarrow 0$.  Can anyone give me some hints to solve this problem? Thank you! Fetch the row which has the Max value for a column What can cause "System.CalloutException: You have uncommitted work pending. Please commit or rollback before calling out"? What else, other than insert/update/upsert/delete, can cause "System.CalloutException: You have uncommitted work pending. Please commit or rollback before calling out"?  I've search the debug logs multiple times, and there absolutely is not a DML statement executed between the startTest and the failing callout.  Are there any other commands, or perhaps another callout (even though it's only an inquiry), that can cause this?  Does anyone know how to get around this problem? How to calculate the difference between two dates using PHP? I have two dates of the form:  Start Date: 2007-03-24  End Date: 2009-06-26   Now I need to find the difference between these two in the following form:  2 years, 3 months and 2 days   How can I do this in PHP? Include prior knowledge in regression model I've a classical dataset with real attributes and I want to perform a regression.  But, not all the entries in the training dataset are trustworthy; there is an attribute that I can turn into a confidence value (between 0 and 1) to say how much I can trust the label value. For example, if the confidence value is 0, I mustn't take the entry into consideration.  Is there a way to do this? Equivalent of typedef in C# Is there a typedef equivalent in C#, or someway to get some sort of similar behaviour? I've done some googling, but everywhere I look seems to be negative. Currently I have a situation similar to the following:  class GenericClass&lt;T&gt;  {     public event EventHandler&lt;EventData&gt; MyEvent;     public class EventData : EventArgs { /* snip */ }     // ... snip }   Now, it doesn't take a rocket scientist to figure out that this can very quickly lead to a lot of typing (apologies for the horrible pun) when trying to implement a handler for that event. It'd end up being something like this:  GenericClass&lt;int&gt; gcInt = new GenericClass&lt;int&gt;; gcInt.MyEvent += new EventHandler&lt;GenericClass&lt;int&gt;.EventData&gt;(gcInt_MyEvent); // ...  private void gcInt_MyEvent(object sender, GenericClass&lt;int&gt;.EventData e) {     throw new NotImplementedException(); }   Except, in my case, I was already using a complex type, not just an int. It'd be nice if it were possible to simplify this a little...  Edit: ie. perhaps typedefing the EventHandler instead of needing to redefine it to get similar behaviour. I'm not quite sure how the total attack bonus interacts with BAB.   Can you make more attacks than shown by your BAB (e.g. +11/+6/+1 BAB allows you to make 3 attacks) by having a high enough DEX, STR or other attack bonus modifiers? Assuming I have +11/+6/+1 BAB, and a spell gives me +6 attack bonus, would that make me able to attack as if I had +17/+12/+7/+2 BAB, giving me an extra attack?)   Can you make multiple attacks even if you have one of your stats drained, making your attack bonus negative, or less than 5?      It says in the SRD that the formula for attack bonus in melee is this:       Base attack bonus + Strength modifier + size modifier   I've also been told that you can make multiple attacks in one turn, but each attack gains a -5 penalty to attack bonus. Why is the application of probability in  (QM) fundamentally different from its application in other areas? QM applies probability according to the same  as in other areas of physics, engineering, etc.  Why is there a difference?  Naively one would assume one of these possibilities:   It is not the same probability (theory?) It is a matter of interpretation (of the formalism?) Something else?   Many answers (which I am still studying) focus on the fact that the combined probability of two mutually-exclusive events in QM is not equal to the sum of the probabilities of each event (which holds classically by definition). This fact (appears to) makes the formulation of another probability (a quantum one) a necessity.   Yet this again breaks down to assumed independent, if this is not so, the "classic probability" is applicable (as indeed in other areas). This is one of the main points of the question. How to allow Page Up in GNU Screen? I use Vim to edit text files on Linux. Commonly I connect to remote Linux machines using PuTTY from Windows.  I use GNU Screen commonly as well.  When using Vim inside Screen I am unable to use the Page Up key because Screen interprets it as a command to start copy mode.    I would like to use Page Up for its regular up-paging functionality.  How can I configure Screen to do this? Prove the following inequality:   $$\dfrac{e^x + e^{-x}}2 \le e^{\frac{x^2}{2}}$$   This should be solved using Taylor series.  I tried expanding the left to the 5th degree and the right site to the 3rd degree, but it didn't help.  Any tips? Apache error "Could not reliably determine the server's fully qualified domain name" When I restart my Apache server using the command  sudo /etc/init.d/apache2 restart   I get the following error:  Restarting web server apache2 apache2: Could not reliably determine the server's fully qualified domain name, using 127.0.1.1 for ServerName ... waiting apache2: Could not reliably determine the server's fully qualified domain name, using 127.0.1.1 for ServerName   Is the server using 127.0.1.1 instead of 127.0.0.1? What causes this error? Sources missing in /etc/apt/sources.list, how do I get them back? Let A,B be in $M_{mxn}(\mathbb{R})$  Prove that if rank(A + B) = rank(A) + rank(B), then col(A) ∩ col(B) = {0}  I started with a proof by contradiction, since we know that rank(A + B) ≤ rank(A) + rank(B). I assume that if rank(A + B) &lt; rank(A) + rank(B), then col(A) ∩ col(B) = {0}. I realize that we don't have to do the > case. However I am a little confused on how to show col from rank. How To Use DateTimePicker In WPF? I have no idea how to use the DateTimePicker control in WPF. It is not available in the Toolbox. Proof of $(a+b)^{n+1}$ I have to do proof of $(a+b)^n$ and $(a+b)^{n+1}$ with mathematical induction.  I finished the first one $(a+b)^n = a^n + na^{n-1}b+\dots+b^n$.  I however have trouble with the second one, I don't know what to start exactly. Any help/hints? Express the complex numbers given in Problem in the form $a+ib$ TestMethod do not support Web service callouts, test skipped Beamer continue block in next column A continuation of .  I'm fighting a page-limit in a single-column layout and I need to put a Figure and a Table side-by-side and provide them with independent captions. However, the style guide for the publishers (LNCS) wants Figure captions below and Table captions above (probably something to do with ).   =======================================================  If I adapt @lockstep's floatrow example from  accordingly to have a Table caption above ...  \documentclass{article}  \usepackage{floatrow} % Table float box with bottom caption, box width adjusted to content  %% ********************************** %% just adding \captop to original example %% ********************************** \newfloatcommand{capbtabbox}{table}[\captop][\FBwidth]  \usepackage{blindtext}   \begin{document}  \blindtext  \begin{figure} \begin{floatrow} \ffigbox{%   \rule{3cm}{3cm}% }{%   \caption{A figure}% } \capbtabbox{%   \begin{tabular}{cc} \hline   Author &amp; Title \\ \hline   Knuth &amp; The \TeX book \\   Lamport &amp; \LaTeX \\ \hline   Knuth &amp; The \TeX book \\   Lamport &amp; \LaTeX \\ \hline   Knuth &amp; The \TeX book \\   Lamport &amp; \LaTeX \\ \hline   \end{tabular} }{%   \caption{A table}% } \end{floatrow} \end{figure}  \end{document}   =======================================================  The problem becomes clear ...    =======================================================  The floatrow doesn't correctly line up the Table and Caption. I reluctantly tried to use vspace to solve the problem, but it didn't work out.  Any suggestions on how to get these two to align? I'm happy to accept any alignment that ensures that the Table and Figure fit within the same "box".  (A similar-ish question was , but specific for subfig and with a very localised problem it seems.) How to count number of distinct values in a range?