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merging multiple columns into one columns in pandas

由 好久不见. 提交于 2019-12-07 14:55:41
问题 I have a dataframe called ref(first dataframe) with columns c1, c2 ,c3 and c4. ref= pd.DataFrame([[1,3,.3,7],[0,4,.5,4.5],[2,5,.6,3]], columns=['c1','c2','c3','c4']) print(ref) c1 c2 c3 c4 0 1 3 0.3 7.0 1 0 4 0.5 4.5 2 2 5 0.6 3.0 I wanted to create a new column i.e, c5 ( second dataframe) that has all the values from columns c1,c2,c3 and c4. I tried concat, merge columns but i cannot get it work. Please let me know if you have a solutions? 回答1: You can use unstack for creating Series from

Are const arrays declared within a function stored on the stack?

由 梦想的初衷 提交于 2019-12-07 13:09:18
问题 if this was declared within a function, would it be declared on the stack? (it being const is what makes me wonder) void someFunction() { const unsigned int actions[8] = { e1, e2, etc... }; } 回答1: Yes, they're on the stack. You can see this by looking at this code snippet: it will have to print the destruction message 5 times. struct A { ~A(){ printf( "A destructed\n" ); } }; int main() { { const A anarray [5] = {A()} ; } printf( "inner scope closed\n"); } 回答2: As I understand it: yes. I've

How java works in android through memory object heap allocation

由 不羁岁月 提交于 2019-12-07 12:53:50
问题 I am new to Android but experienced in Java . In Java when we do this: MyClass myObj = new MyClass(); It clearly does the following: Inserts the memory pointer myObj upto the stack Allocates a new space for object of type MyClass in the heap Appoints this new space's reference to myObj But I am a little bit confused about the following questions: But in Android , does this work in the same way? Does Android have full stack and heap memories? Does Android have Java Virtual Machine (JVM) for my

Is finding code's address in visual studio 2010 c++ using in-line assembly possible?

由 假如想象 提交于 2019-12-07 12:16:48
问题 Lets say I want to write an inline assembly function in a c++ code that returns its return address. So if I'm calling the function returnAddress() from some address and it needs to return to the address X after the function is done, I want returnAddress() to return the value X. example of code for returnAddress(): void* getAddress() { __asm { pop ebx; // moving return offset to ebx? push ebx; // restoring stack state xor eax, eax; mov ax, cs; // ax <- code segment mov ecx, 16; mul ecx; //

java inheritance versus composition (implementing a stack)

由 落爺英雄遲暮 提交于 2019-12-07 11:56:50
问题 I am trying to implement a Stack in java (using the list interface: Interface List). I want to implement it two different ways: using composition and inheritance. For inheritance, so far I have: import java.util.Collection; import java.util.Iterator; import java.util.List; import java.util.ListIterator; public class StackInheritance implements List { //implement list methods } For composition, I have: import java.util.List; public abstract class StackComposition implements List { // implement

Erlang: How to limit the memory assigned to a process

由 北战南征 提交于 2019-12-07 10:43:37
问题 What I'm asking is if it's possible to limit memory (heap or stack) assigned to a specific process, so that this process can't exceed it. Maybe something like "process_flag(min_heap_size, MinHeapSize)", but for the maximum heap. 回答1: You could put together some kind of process tracking gen_server that periodically checks assigned processes for memory footprint and kills them if it exceeds a certain amount. Using a combination of process_info(Pid, memory). and exit(Pid, Reason) calls, this

Javascript string stored on stack

由 早过忘川 提交于 2019-12-07 09:31:00
问题 I'm reading Professional JavaScript for Web Developers 3rd ed. and in the summary of chapter 4 one can read: Two types of values can be stored in JavaScript variables: primitive values and reference values. Primitive values have one of the five primitive data types: Undefined, Null, Boolean, Number, and String. Primitive and reference values have the following characteristics: Primitive values are of a fixed size and so are stored in memory on the stack. But I can have different strings, say:

Is it possible to force JVM to create an object in stack other than heap?

由 这一生的挚爱 提交于 2019-12-07 09:10:23
问题 I read some where that sometimes JVM will identify some objects and try to create it in stack than heap as the memory allocation on the stack is cheaper than the memory allocation in the heap, deallocation on the stack is free and the stack is efficiently managed by the run-time. So is how this object allocation in stack works and is there any way to force the JVM to do this ? 回答1: There is no way to force the JVM to allocate objects anywhere. You should not care where Java actually allocates

Stack size on BlackBerry?

由 ぐ巨炮叔叔 提交于 2019-12-07 09:01:13
问题 I know that on Symbian stack size is equal to 8k. What about BlackBerry? 回答1: Perhaps this thread on the BlackBerry Forums is helpful: I don't believe there is any way to [ increase stack size for threads ] in the BB environment. Stack Size is initialized by the JVM, and we have no access to JVM parameters in the BB OS, AFAIK. 来源： https://stackoverflow.com/questions/1267075/stack-size-on-blackberry

Segmentation fault for pthreads in a recursive call

由 夙愿已清 提交于 2019-12-07 08:39:20
Given the code below, I get a segmentation fault if I run it with n>16. I think it has something to do with the stack, but I can't figure it out. Could anyone give me a hand? The code is not mine, and really not important. I would just like someone to give me a hand with what is happening. This SO question is very similar, but there's not enough information (the person who posts the answer briefly talks about the problem, but then goes on to talk about a different language). Besides, notice that with two gigs and no recursion, I can (if I'm doing it right) successfully create more than 16000
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