大约有 40,000 项符合查询结果（耗时：0.0555秒） [XML]
A Regex that will never be matched by anything
...
This is actually quite simple, although it depends on the implementation / flags*:
$a
Will match a character a after the end of the string. Good luck.
WARNING:
This expression is expensive -- it will scan the entire line, find the en...
In Python how should I test if a variable is None, True or False
...
a = 'foo' if a: print 'its true' a is not actually TRUE, it's just not none
– wesm
Apr 3 '15 at 21:06
...
pandas GroupBy columns with NaN (missing) values
...n the Missing Data section of the docs:
NA groups in GroupBy are automatically excluded. This behavior is consistent with R, for example.
One workaround is to use a placeholder before doing the groupby (e.g. -1):
In [11]: df.fillna(-1)
Out[11]:
a b
0 1 4
1 2 -1
2 3 6
In [12]: df.fil...
Check if URL has certain string with PHP
...URL and the rest check if it contains the word "car".
$url = 'http://' . $_SERVER['SERVER_NAME'] . $_SERVER['REQUEST_URI'];
if (strpos($url,'car') !== false) {
echo 'Car exists.';
} else {
echo 'No cars.';
}
shar...
搭建高可用mongodb集群（一）——配置mongodb - 大数据 & AI - 清泛网 - 专...
...安装程序包
wget http://fastdl.mongodb.org/linux/mongodb-linux-x86_64-2.4.6.tgz
#解压下载的压缩包
tar xvzf mongodb-linux-x86_64-2.4.6.tgz
#进入mongodb程序执行文件夹
cd mongodb-linux-x86_64-2.4.6/bin/
3、启动单实例mongodb
mongod --dbpath /data/mongodbtest/...
How to update Python?
I have version 2.7 installed from early 2012. I can't find any consensus on whether I should completely uninstall and wipe this version before putting on the latest version.
...
'UserControl' constructor with parameters in C#
Call me crazy, but I'm the type of guy that likes constructors with parameters (if needed), as opposed to a constructor with no parameters followed by setting properties. My thought process: if the properties are required to actually construct the object, they should go in the constructor. I get two...
Does Go have “if x in” construct similar to Python?
...ion without separate methods for every single type
– Allen
May 13 '15 at 4:33
29
It could be done...
How can I add or update a query string parameter?
... @JarónBarends - Tweak value check to check against undefined and null to allow setting 0 values
Third Update
There was a bug where removing a querystring variable directly before a hashtag would lose the hashtag symbol which has been fixed
Fourth Update
Thanks @rooby for pointing out a regex o...
Is gcc std::unordered_map implementation slow? If so - why?
...2531
get : 1565
So std::unordered_map in gcc-4.7 is broken (or my installation, which is an installation of gcc-4.7.0 on Ubuntu - and another installation which is gcc 4.7.1 on debian testing).
I will submit a bug report.. until then: DO NOT use std::unordered_map with gcc 4.7!
...