No error , No gain

Anyone tinkering with Python long enough has been bitten (or torn to pieces) by the following issue: def foo(a=[]): a.append(5) return a Python novices would expect this function to always return a list with only one element: [5]. The result is instead very different, and very astonishing (for a novice): >>> foo() [5] >>> foo() [5, 5] >>> foo() [5, 5, 5] >>> foo() [5, 5, 5, 5] >>> foo() A manage..

How do I copy a folder from remote to local host using scp? I use ssh to log in my server. Then, I would like to copy the remote folder foo to local /home/user/Desktop. How do I achieve this? scp -r user@your.server.example.com:/path/to/foo /home/user/Desktop/ By not including the trailing '/' at the end of foo, you will copy the directory itself (including contents), rather than only the conten..

How do you disable autocomplete in the major browsers for a specific input (or form field)? Firefox 30 ignores autocomplete="off" for passwords, opting to prompt the user instead whether the password should be stored on the client. Note the following commentary from May 5, 2014: The password manager always prompts if it wants to save a password. Passwords are not saved without permission from th..

How can I change the class of an HTML element in response to an onclick or any other events using JavaScript? Modern HTML5 Techniques for changing classes Modern browsers have added classList which provides methods to make it easier to manipulate classes without needing a library: document.getElementById("MyElement").classList.add('MyClass'); document.getElementById("MyElement").classList.remove..

I would like to upload a file asynchronously with jQuery. $(document).ready(function () { $("#uploadbutton").click(function () { var filename = $("#file").val(); $.ajax({ type: "POST", url: "addFile.do", enctype: 'multipart/form-data', data: { file: filename }, success: function () { alert("Data Uploaded: "); } }); }); }); File Instead of the file being uploaded, I am only getting the filename. ..

I created a local branch which I want to 'push' upstream. There is a similar question here on Stack Overflow on how to track a newly created remote branch. However, my workflow is slightly different. First I want to create a local branch, and I will only push it upstream when I'm satisfied and want to share my branch. How would I do that? (my google searches did not seem to come up with anything..

How can an int be cast to an enum in C#? From an int: YourEnum foo = (YourEnum)yourInt; From a string: YourEnum foo = (YourEnum) Enum.Parse(typeof(YourEnum), yourString); // The foo.ToString().Contains(",") check is necessary for enumerations marked with an [Flags] attribute if (!Enum.IsDefined(typeof(YourEnum), foo) && !foo.ToString().Contains(",")) { throw new InvalidOperationException($"{your..

If I have an object implementing the Map interface in Java and I wish to iterate over every pair contained within it, what is the most efficient way of going through the map? Will the ordering of elements depend on the specific map implementation that I have for the interface? Map map = ... for (Map.Entry entry : map.entrySet()) { System.out.println(entry.getKey() + "/" + entry.getValue()); } On..

I have an object x. I'd like to copy it as object y, such that changes to y do not modify x. I realized that copying objects derived from built-in JavaScript objects will result in extra, unwanted properties. This isn't a problem, since I'm copying one of my own literal-constructed objects. How do I correctly clone a JavaScript object? To do this for any object in JavaScript will not be simple o..

How do I check if a particular key exists in a JavaScript object or array? If a key doesn't exist, and I try to access it, will it return false? Or throw an error? Checking for undefined-ness is not an accurate way of testing whether a key exists. What if the key exists but the value is actually undefined? var obj = { key: undefined }; obj["key"] !== undefined // false, but the key exists! You s..

I know how to make a new branch that tracks remote branches, but how do I make an existing branch track a remote branch? I know I can just edit the .git/config file, but it seems there should be an easier way. Given a branch foo and a remote upstream: As of Git 1.8.0: git branch -u upstream/foo Or, if local branch foo is not the current branch: git branch -u upstream/foo foo Or, if you like to t..

I would like to know how to delete a commit. By delete, I mean it is as if I didn't make that commit, and when I do a push in the future, my changes will not push to the remote branch. I read git help, and I think the command I should use is git reset --hard HEAD. Is this correct? Careful: git reset --hard WILL DELETE YOUR WORKING DIRECTORY CHANGES. Be sure to stash any local changes you want to..

How can I stash only one of multiple changed files on my branch? git stash push -p -m "my commit message" -p let's you select the hunks that should be stashed; whole files can be selected as well. You'll be prompted with a few actions for each hunk: y - stash this hunk n - do not stash this hunk q - quit; do not stash this hunk or any of the remaining ones a - stash this hunk and all later hunks..

This question's answers are a community effort. Edit existing answers to improve this post. It is not currently accepting new answers or interactions. How can I list all files of a directory in Python and add them to a list? os.listdir() will get you everything that's in a directory - files and directories. If you want just files, you could either filter this down using os.path: from os import l..

Given a list ["foo", "bar", "baz"] and an item in the list "bar", how do I get its index (1) in Python? >>> ["foo", "bar", "baz"].index("bar") 1 Reference: Data Structures > More on Lists Caveats follow Note that while this is perhaps the cleanest way to answer the question as asked, index is a rather weak component of the list API, and I can't remember the last time I used it in anger. It's bee..

I've always been one to simply use: List names = new ArrayList(); I use the interface as the type name for portability, so that when I ask questions such as these I can rework my code. When should LinkedList be used over ArrayList and vice-versa? Summary ArrayList with ArrayDeque are preferable in many more use-cases than LinkedList. If you're not sure — just start with ArrayList. TLDR, in Array..

I've used the following script to see if a file exists: #!/bin/bash FILE=$1 if [ -f $FILE ]; then echo "File $FILE exists." else echo "File $FILE does not exist." fi What's the correct syntax to use if I only want to check if the file does not exist? #!/bin/bash FILE=$1 if [ $FILE does not exist ]; then echo "File $FILE does not exist." fi The test command ([ here) has a "not" logical operator w..

In Java, are there clear rules on when to use each of access modifiers, namely the default (package private), public, protected and private, while making class and interface and dealing with inheritance? The official tutorial may be of some use to you. Class Package Subclass (same pkg) Subclass (diff pkg) World public + + + + + protected + + + + no modifier + + + private + + : accessible blank :..

I have an array of JavaScript objects: var objs = [ { first_nom: 'Lazslo', last_nom: 'Jamf' }, { first_nom: 'Pig', last_nom: 'Bodine' }, { first_nom: 'Pirate', last_nom: 'Prentice' } ]; How can I sort them by the value of last_nom in JavaScript? I know about sort(a,b), but that only seems to work on strings and numbers. Do I need to add a toString() method to my objects? It's easy enough to writ..

I saw this question, but I didn't see a JavaScript specific example. Is there a simple string.Empty available in JavaScript, or is it just a case of checking for ""? If you just want to check whether there's a truthy value, you can do: if (strValue) { //do something } If you need to check specifically for an empty string over null, I would think checking against "" is your best bet, using the ==..