prepend | 易学教程

Prepend a line to an existing file in Python

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I need to add a single line to the first line of a text file and it looks like the only options available to me are more lines of code than I would expect from python. Something like this: f = open('filename','r') temp = f.read() f.close() f = open('filename', 'w') f.write("#testfirstline") f.write(temp) f.close() Is there no easier way? Additionally, I see this two-handle example more often than opening a single handle for reading and writing ('r+') - why is that? Python makes a lot of things easy and contains libraries and wrappers for a lot of common operations, but the goal is not to hide

How can I implement prepend and append with regular JavaScript?

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How can I implement prepend and append with regular JavaScript without using jQuery? Grumdrig Perhaps you're asking about the DOM methods appendChild and insertBefore . parentNode.insertBefore(newChild, refChild) Inserts the node newChild as a child of parentNode before the existing child node refChild . (Returns newChild .) If refChild is null, newChild is added at the end of the list of children. Equivalently, and more readably, use parentNode.appendChild(newChild) . Here's a snippet to get you going: theParent = document.getElementById("theParent"); theKid = document.createElement("div");

jquery - keep window from changing scroll position while prepending items to a list?

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问题 I have a page that displays messages and I want it to work just like Facebook, but without the lazy loader. Messages are displayed in chronological order, most recent last. My message list is initially populated x number of most recent messages, and the window is scrolled to the bottom. When the user starts to read the thread, they read from bottom to top. If they get to the top, they can load more messages... I make them click a button... facebook has a lazy loader. New messages are

Unix command to prepend text to a file

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问题 Is there a Unix command to prepend some string data to a text file? Something like: prepend \"to be prepended\" text.txt 回答1: sed -i.old '1s;^;to be prepended;' inFile -i writes the change in place and take a backup if any extension is given. (In this case, .old ) 1s;^;to be prepended; substitutes the beginning of the first line by the given replacement string, using ; as a command delimiter. 回答2: printf '%s\n%s\n' "to be prepended" "$(cat text.txt)" >text.txt 回答3: Process Substitution I'm

What's the idiomatic syntax for prepending to a short python list?

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问题 list.append() is the obvious choice for adding to the end of a list. Here\'s a reasonable explanation for the missing list.prepend() . Assuming my list is short and performance concerns are negligible, is list.insert(0, x) or list[0:0] = [x] idiomatic? 回答1: The s.insert(0, x) form is the most common. Whenever you see it though, it may be time to consider using a collections.deque instead of a list. 回答2: If you can go the functional way, the following is pretty clear new_list = [x] + your_list

.append(), prepend(), .after() and .before()

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问题 I am pretty proficient with coding, but now and then I come across code that seems to do basically the same thing. My main question here is, why would you use .append() rather then .after() or vice verses? I have been looking and cannot seem to find a clear definition of the differences between the two and when to use them and when not to. What are the benefits of one over the other and also why would i use one rather then the other?? Can someone please explain this to me? var txt = $(\'#\' +

Adding code to a javascript function programmatically

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问题 I\'m attempting to customize an existing JS library without modifying the original JS code. This code loads in a few external JS files which I do have access to, and what I\'d like to do is change one of the functions contained in the original file without copying and pasting the whole thing into the second JS file. So for example, the off limits JS might have a function like this: var someFunction = function(){ alert(\"done\"); } I\'d like to be able to somehow append or prepend some JS code

Prepend a line to an existing file in Python

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问题 I need to add a single line to the first line of a text file and it looks like the only options available to me are more lines of code than I would expect from python. Something like this: f = open(\'filename\',\'r\') temp = f.read() f.close() f = open(\'filename\', \'w\') f.write(\"#testfirstline\") f.write(temp) f.close() Is there no easier way? Additionally, I see this two-handle example more often than opening a single handle for reading and writing (\'r+\') - why is that? 回答1: Python

How can I implement prepend and append with regular JavaScript?

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问题 How can I implement prepend and append with regular JavaScript without using jQuery? 回答1: Perhaps you're asking about the DOM methods appendChild and insertBefore . parentNode.insertBefore(newChild, refChild) Inserts the node newChild as a child of parentNode before the existing child node refChild . (Returns newChild .) If refChild is null, newChild is added at the end of the list of children. Equivalently, and more readably, use parentNode.appendChild(newChild) . 回答2: Here's a snippet to