when I initialize an array in python like so and then assign an element to a different value and then print out the 2d list  dist = [[0]*3]*3 dist[1][1] = 1   It gives me this  [[0,1,0],[0,1,0],[0,1,0]]   Can someone explain to me why the whole column has changed instead of just the specific element?
410
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?
22625
MyClass[] array; List&lt;MyClass&gt; list;   What are the scenarios when one is preferable over the other? And why?
74245
In the  book on pg 130, they mention that an Array's length is fixed when you initialize it and that multidimensional arrays are not supported. I just tried using the .add function on an array and it worked so I'm sure what they are talking about, but I couldn't make an array of arrays (which could have just been because I didn't have the right syntax). Ignoring syntax errors, there seems to be some sort of difference and thus maybe an (even if just slight) advantage to using one over the other?
5148
I have recently been thinking about the difference between the two ways of defining an array:   int[] array int array[]   Is there a difference?
72069
Given [1,2,3,4,5], how can I do something like   1/1, 1/2, 1/3,1/4,1/5, ...., 3/1,3/2,3/3,3/4,3/5,.... 5/1,5/2,5/3,5/4,5/5   I would like to store all the results, find the minimum, and return the two numbers used to find the minimum. So in the case I've described above I would like to return (1,5).  So basically I would like to do something like  for each element i in the list map some function across all elements in the list, taking i and j as parameters store the result in a master list, find the minimum value in the master list, and return the arguments i, jused to calculate this minimum value.  In my real problem I have a list objects/coordinates, and the function I am using takes two coordinates and calculates the euclidean distance. I'm trying to find minimum euclidean distance between any two points but I don't need a fancy algorithm.
101020
I would like to sort a matrix according to a particular column. There is a sort function, but it sorts all columns independently.  For example, if my matrix data is:   1     3  5     7 -1     4   Then the desired output (sorting by the first column) would be:  -1     4  1     3  5     7   But the output of sort(data) is:  -1     3  1     4  5     7   How can I sort this matrix by the first column?
109666
What is the best way to copy a list? I know the following ways, which one is better? Or is there another way?  lst = ['one', 2, 3]  lst1 = list(lst)  lst2 = lst[:]  import copy lst3 = copy.copy(lst)
90115
I am trying to create an array of pointers. These pointers will point to a Student object that I created. How do I do it? What I have now is:   Student * db = new Student[5];   But each element in that array is the student object, not a pointer to the student object. Thanks.
15363
If you are creating a 1d array in Python is there any benefit to using the NumPy package?
60165
How can we read and write values in a multidimensional array in verilog, i had read in  regarding different operations that can be done on multidimensional array. like if there is a part of code like this  input [15:0] me;  reg [15:0] p_array [7:0]; reg abc_pqr [2:0];  abc_pqr[0] &lt;= me[0]; abc_pqr[1] &lt;= me[1]; abc_pqr[2] &lt;= me[1]; p_array[abc_pqr[0]] &lt;= me[0]; p_array[abc_pqr[1]] &lt;= me[1]; p_array[abc_pqr[2]] &lt;= me[2];   so is this code will work and will not produce any error?  What is the difference between these two while assigning value  "&lt;=" and "=", i had seen "&lt;=" in most of the places during passing values.
100626
For example {a..c}{1..3} expands to a1 a2 a3 b1 b2 b3 c1 c2 c3.   If I wanted to print a1 b1 c1 a2 b2 c2 a3 b3 c3, is there an analogous way to do that? What's the simplest way?
94558
\documentclass[12pt]{article}  \usepackage{amsmath,amsthm,amssymb,amsfonts} \usepackage{enumerate}  \newenvironment*{exercise}{}  \newcommand{\R}{\mathbb{R}}  \begin{document}  \begin{exercise}{1.10.} Show that $B=\{[a,b)\subset\R|a&lt;b\}$ is a basis for a topology on $\R$.\\ \begin{enumerate} \item{stuff...} \item{stuff...} \end{enumerate} \end{exercise}  \end{document}   My main concern is that the list numbers in the list and the text in the instructions line up. That is that the S in show is lined up with the 1 and 2 etc in the list.
70618
So I was writing up a simple binary tree in Python and came across [...]  I don't believe this to be related to the Ellipsis object, more it seems to have something to do with an infinity loop (due to Python's shallow copy?). The source of this infinity loop and why it doesn't get expanded while expanding when accessed is something I'm completely lost to, however   &gt;&gt;&gt; a [[[[[], [], 8, 3], [[], [], 3, 2], 6, 3], [], 1, 4], [[], [], -4, 2], 0, 0] &gt;&gt;&gt; Keys(a)#With a+b [0, 1, 6, 8, 3, -4] &gt;&gt;&gt; Keys(a)#With [a,b] [8, [...], [...], 3, [...], [...], 6, [...], [...], 1, [...], [...], -4, [...], [...], 0, [...], [...]] &gt;&gt;&gt; Keys(a)[1]#?? [8, [...], [...], 3, [...], [...], 6, [...], [...], 1, [...], [...], -4, [...], [...], 0, [...], [...], 8, [...], [...], 3, [...], [...], 6, [...], [...], 1, [...], [...], -4, [...], [...], 0, [...], [...]]     Version using a+b  def Keys(x,y=[]):     if len(x):y+=[x[2]]+Keys(x[0],y)+Keys(x[1],y)#Though it seems I was using y=y[:]+, this actually outputs an ugly mess     return y   version using [a,b]  def Keys(x,y=[]):     if len(x):y+=[x[2],Keys(x[0],y),Keys(x[1],y)]     return y   So what exactly is [...]?
43660
I have a list of structs and I want to change one element. For example :  MyList.Add(new MyStruct("john"); MyList.Add(new MyStruct("peter");   Now I want to change one element:  MyList[1].Name = "bob"   However, whenever I try and do this I get the following error:     Cannot modify the return value of   System.Collections.Generic.List.this[int]‘ because it is not   a variable   If I use a list of classes, the problem doesn't occur.  I guess the answer has to do with structs being a value type.  So, if I have a list of structs should I treat them as read-only? If I need to change elements in a list then I should use classes and not structs?
1890
From the :  [1,4,9].map(Math.sqrt)   will yield:  [1,2,3]   Why then does this:  ['1','2','3'].map(parseInt)   yield this:  [1, NaN, NaN]   I have tested in Firefox 3.0.1 and Chrome 0.3 and just as a disclaimer, I know this is not cross-browser functionality (no IE).  I found out that the following will accomplish the desired effect. However, it still doesn’t explain the errant behavior of parseInt.  ['1','2','3'].map(function(i){return +i;}) // returns [1,2,3]
23113
What's the difference?  What are the advantages / disadvantages of tuples / lists?
42368
I have a python list, say l  l = [1,5,8]   I want to write a sql query to get the data for all the elements of the list, say  select name from students where id = |IN THE LIST l|   How do I accomplish this?