reference

问题 First I wrote the first sample of code and it didn't work correctly. I prefer the first sample, but only the second one works correctly. I don't know why the first sample doesn't change the original array but second does. Where is the difference? First sample: import heapq def heap_sort(tab): heap = [] for i in tab: heapq.heappush(heap, i) tab = [heapq.heappop(heap) for _ in xrange(len(heap))] temp_tab = [4, 3, 5, 1] heap_sort(temp_tab) print temp_tab Prints: [4, 3, 5, 1] Second sample:

问题 Assignment: >>> a = ['spam'] >>> b = ['spam'] >>> a is b False Reference: >>> c = ['spam'] >>> d = c >>> c is d True What is the difference between above both? Why assignment results False ? Why reference results True ? 回答1: Your first snippet creates two unique list objects, which are not the same. Hence a is b returns false because a and b are pointing to distinct objects: +------+ a ------> | list | +------+ +------+ b ------> | list | +------+ Your second snippet creates a single list

问题 Assignment: >>> a = ['spam'] >>> b = ['spam'] >>> a is b False Reference: >>> c = ['spam'] >>> d = c >>> c is d True What is the difference between above both? Why assignment results False ? Why reference results True ? 回答1: Your first snippet creates two unique list objects, which are not the same. Hence a is b returns false because a and b are pointing to distinct objects: +------+ a ------> | list | +------+ +------+ b ------> | list | +------+ Your second snippet creates a single list

问题 I have got a couple of functions that manipulate data in an array, for example unset_data() you pass it the value and an unlimited amount of string args like: unset_data( $my_array, "firstname", "password" ); and it can handle multi-dimentional arrays etc, quite simple. But should this function use a reference to the array and change it directly? Or should i return the new array with the values unset. I can never decide whether a function should use reference or not, Is there like, specific

问题 I am inserting 2-dimensional array references into my heap in Perl. How should I define the 'elements' attribute when constructing my heap so that I can properly use my comparator function? my $heap = Heap::Simple->new( order => \&byNumOrStr, elements => [Array => 0] ); sub byNumOrStr { my ( $a, $b ) = @_; $b->[0] <=> $a->[0] #0-th element is a number. || $a->[1] cmp $b->[1]; #1-st element is a number } I keep getting back this error: Can't use string ("2.55") as an ARRAY ref while "strict

问题 I was trying repository pattern with ASP.Net 5 project and service project. I referenced my " .Service" class library project into my " .Web" project but something went wrong with the reference. I removed all referenced to other libraries, even removed my " .Service" and " .Web" projects and added new empty ones but the newly created " .Web" project still referencing the old version of deleted " .Service" project. " .Web" > ASP.Net 5 project. " .Service" > .Net Framework 4.5.1 class library

问题 I am very new to programming, but have been following c++ tutorials and amassing a number of PDFs for the last week or so to help me out. I couldn't find anything in them or online that answered my question clearly enough. Please forgive me for my newbie-ness. Pertinent code: Logfile.hpp // =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= // HEADER :: CLASS INTERFACE FILE // ============================== // Include Guard #ifndef __LOGFILE_INCLUDED__ // If Actor.hpp hasn't been

问题 i have following code: def mymethod(a) a.replace("a") end mystring = "b" mymethod(mystring) p mystring # => "a" but i want to perform same with Integer is that possible? 回答1: Short answer: no. Long answer: no, it's not possible. Integer is a type primitive enough to not have state (and state modifying operations). Every operation on integer generates a new integer. Probably , if you drop down to C level, you could be able to modify underlying value in-place. But I'm not sure. Anyway, this

问题 In my WPF MVVM Project I have a button that triggers a function that should add a node to a xml and then set the focus to a textbox. My question is, how can i receive a reference to a control? View: <Button Command="{Binding Path=ButtonAddCategory_Click}" /> ViewModel: RelayCommand buttonAddCategory_Click; public ICommand ButtonAddCategory_Click { get { return buttonAddCategory_Click ?? (buttonAddCategory_Click = new RelayCommand(param => this.AddCategory(), param => true)); } } public void

问题 I had to switch from .net 4.5 to .net 4.0 because some of my customers still use WinXP. Now, after switching, this is the error I'm getting: Could not load file or assembly 'System.Data.SQLite, Version=1.0.66.0, Culturre-neutral, PublicKeyToken=db937bc2d44ff139' or one of its dependencies. An attempt was made to load a program with an incorrect format. I haven't been able to find a solution for this, but here's what I tried so far: Switch back to 4.5 - Didn't work Add the reference again -