大约有 40,000 项符合查询结果（耗时：0.0390秒） [XML]
Repeat Character N Times
In Perl I can repeat a character multiple times using the syntax:
23 Answers
23
...
What's up with Java's “%n” in printf?
I'm reading Effective Java and it uses %n for the newline character everywhere. I have used \n rather successfully for newline in Java programs.
...
Pandas dataframe get first row of each group
...ourth
If you need id as column:
>>> df.groupby('id').first().reset_index()
id value
0 1 first
1 2 first
2 3 first
3 4 second
4 5 first
5 6 first
6 7 fourth
To get n first records, you can use head():
>>> df.groupby('id').head(2).reset_index(drop...
How to match “any character” in regular expression?
...ncode this is with a character class whose members form a partition of the set of all possible characters.
Usually people write that as [\s\S] (whitespace or non-whitespace), though [\w\W], [\d\D], etc. would all work.
shar...
Applying .gitignore to committed files
...dex --no-assume-unchanged <file>
to find out which files have been set this way:
git ls-files -v|grep '^h'
credit for the original answer to
http://blog.pagebakers.nl/2009/01/29/git-ignoring-changes-in-tracked-files/
...
Best cross-browser method to capture CTRL+S with JQuery?
My users would like to be able to hit Ctrl + S to save a form. Is there a good cross-browser way of capturing the Ctrl + S key combination and submit my form?
...
Calculating moving average
I'm trying to use R to calculate the moving average over a series of values in a matrix. The normal R mailing list search hasn't been very helpful though. There doesn't seem to be a built-in function in R will allow me to calculate moving averages. Do any packages provide one? Or do I need to writ...
Difference between single and double quotes in Bash
...
@ekiim That exact text is set (unchanged) into PS1. Try echo $PS1 to see what I mean. But PS1 is evaluated before being displayed (see the PROMPTING section in the bash manpage). To test this out, try PS1='$X'. You will have no prompt. Then run X=foo ...
How can I efficiently download a large file using Go?
... editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled) {
StackExchange.using("snippets", function() {
createEditor();
});
}
else {
createEditor();
...
Tricks to manage the available memory in an R session
...kage. With its := operator you can :
Add columns by reference
Modify subsets of existing columns by reference, and by group by reference
Delete columns by reference
None of these operations copy the (potentially large) data.table at all, not even once.
Aggregation is also particularly fast be...