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How to check if the string is empty?
... they are considered false in a Boolean context, so you can just do this:
if not myString:
This is the preferred way if you know that your variable is a string. If your variable could also be some other type then you should use myString == "". See the documentation on Truth Value Testing for ot...
File Upload ASP.NET MVC 3.0
... public ActionResult Index(HttpPostedFileBase file)
{
// Verify that the user selected a file
if (file != null && file.ContentLength > 0)
{
// extract only the filename
var fileName = Path.GetFileName(file.FileName);
// s...
How do I install Maven with Yum?
...-maven/epel-apache-maven.repo -O /etc/yum.repos.d/epel-apache-maven.repo
Now you can install maven like this:
yum install apache-maven
Once done, maven 3 will be installed and mvn -version will show you which version you've got - I had 3.2.1.
This worked perfectly for me on CentOS 6 with one e...
Accessing Object Memory Address
...ch is guaranteed to be unique and
constant for this object during its
lifetime. Two objects with
non-overlapping lifetimes may have the
same id() value. (Implementation note:
this is the address of the object.)
So in CPython, this will be the address of the object. No such guarantee for ...
Get value of a string after last slash in JavaScript
...
When I know the string is going to be reasonably short then I use the following one liner... (remember to escape backslashes)
// if str is C:\windows\file system\path\picture name.jpg
alert( str.split('\\').pop() );
alert pops up ...
How to override the [] operator in Python?
... key):
return key * 2
myobj = MyClass()
myobj[3] #Output: 6
And if you're going to be setting values you'll need to implement the __setitem__ method too, otherwise this will happen:
>>> myobj[5] = 1
Traceback (most recent call last):
File "<stdin>", line 1, in <module...
Kill detached screen session [closed]
...screens directory will not have the 26727.pts-0.devxxx file in it anymore. Now to make sure just type this:
screen -ls
and you should get:
No Sockets found in /tmp/uscreens/S-xxx.
share
...
Parse config files, environment, and command-line arguments, to get a single collection of options
...es it so that,
my_prog --foo=bar
is equivalent to
my_prog @baz.conf
if @baz.conf is,
--foo
bar
You can even have your code look for foo.conf automatically by modifying argv
if os.path.exists('foo.conf'):
argv = ['@foo.conf'] + argv
args = argparser.parse_args(argv)
The format of the...
Python: How do I make a subclass from a superclass?
...
The only reason to avoid super is if you don't understand the differences between how super works in Python, and how super/parent works in other languages. Admittedly this is not obvious to people coming from other languages, but I wouldn't conclude that that...
C++ Lock-free Hazard Pointer（冒险指针） - C/C++ - 清泛网 - 专注C/C++及内核技术
...ount *Ref() {
++cnt_;
return this;
}
void Deref() {
if (--cnt_ == 0) {
delete this;
}
}
private:
std::unique_ptr<T> ptr_;
std::atomic_uint32_t cnt_;
};
仔细观察可以发现：
每一次的读取操作对应引用计数中增加的数值 1；
...