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What is the difference between Python's list methods append and extend?
...
So with extend, each element of the iterable gets appended onto the list. For example:
>>> my_list
['foo', 'bar']
>>> another_list = [1, 2, 3]
>>> my_list.extend(another_list)
>>> my_list
['foo', 'bar', 1, 2, 3]
Keep in mind that a string is an iterable, so if...
What is an undefined reference/unresolved external symbol error and how do I fix it?
...kes place in several steps, as specified by 2.2 (credits to Keith Thompson for the reference):
The precedence among the syntax rules of translation is specified by the following phases [see footnote].
Physical source file characters are mapped, in an implementation-defined manner, to the basic sou...
How disable Copy, Cut, Select, Select All in UITextView
... operations is to create a subclass of UITextView that overrides the canPerformAction:withSender: method to return NO for actions that you don't want to allow:
- (BOOL)canPerformAction:(SEL)action withSender:(id)sender
{
if (action == @selector(paste:))
return NO;
return [super canP...
GET URL parameter in PHP
...you have a scenario like this:
http://www.mydomain.me/index.php?state=California.php#Berkeley
You can treat the named anchor as a query string like this:
http://www.mydomain.me/index.php?state=California.php&city=Berkeley
Then, access it like this:
$Url = $_GET['state']."#".$_GET['city'];...
Setting PayPal return URL and making it auto return?
...lumn.
Under the Selling Online section, click the Update link in the row for Website Preferences.
The Website Payment Preferences page appears
Under Auto Return for Website Payments, click the On radio button to enable Auto
Return.
In the Return URL field, enter the URL to which you want...
Get model's fields in Django
...e is a private attribute and shouldn't be accessed directly? ... Because, for example, the layout of _meta could change in the future and not be a stable API?
...
Create a menu Bar in WPF?
I want to create a menu bar identical to the one in windows forms in my WPF application.
4 Answers
...
How to count the number of set bits in a 32-bit integer?
... will be mostly 0's or mostly 1's then there are very efficient algorithms for these scenarios.
I believe a very good general purpose algorithm is the following, known as 'parallel' or 'variable-precision SWAR algorithm'. I have expressed this in a C-like pseudo language, you may need to adjust it t...
Run a callback only if an attribute has changed in Rails
...
Rails 5.1+
class Page < ActiveRecord::Base
before_save :do_something, if: :will_save_change_to_status_id?
private
def do_something
# ...
end
end
The commit that changed ActiveRecord::Dirty is here: https://github.com/rails/rails/commit/16ae3db5a5c6a08383b9...
逆向工程——二进制炸弹(CSAPP Project) - 操作系统(内核) - 清泛网 - 专注...
...数，于是查到其定义为：int sscanf(const char *str, const char *format,…)，给出一个使用实例：sscanf(“s 1”, “%s %d”, str, &a)，函数返回2（因为接收了2个参数），str为char*类型，保存”s”；a为int类型，保存1。由此，压入栈中的四个地...