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static and templates folder in the apps may should also contain a folder with the name of app ex. blog this is a convention used to prevent namespace pollution, so we reference the files like /blog/base.html rather than /base.html which provides more clarity about the file we are referencing and pre...

The coordinate systems of Matplotlib come very handy when trying to annotate the plots you make. Sometimes you would like to position text relatively to your data, like when trying to label a specific point. Other times you would maybe like to add a text on top of the figure. This can easily be achi...

In order for a program to react to a certain signal, other than using default action, custom signal handler can be installed using sigaction. sigaction receives three arguments - signal to act on, pointer to sigaction_t structure which, if not NULL, is describing new behaviour and pointer to sigacti...

A string is a sequence of character literals. To date, strings are supported by all modern programming languages,1 but there is no consensus between language designers on how strings should be classified. As far as programming language design is concerned there are two primary concerns to take into ...

SELECT DATE('2003-12-31 01:02:03'); The output will be: 2003-12-31

Least squares is a standard approach to problems with more equations than unknowns, also known as overdetermined systems. Consider the four equations: x0 + 2 * x1 + x2 = 4 x0 + x1 + 2 * x2 = 3 2 * x0 + x1 + x2 = 5 x0 + x1 + x2 = 4 We can express this as a matrix multiplication A * x = b: A ...

When rendering a form 'by hand', it can be useful to know if there are fields left to render or not. The function isRendered() from the FormView class returns true if there are still fields left to be rendered to the template. This snippet prints <h3>Extra fields</h3> if there are fiel...

Group Concat is used in MySQL to get concatenated values of expressions with more than one result per column. Meaning, there are many rows to be selected back for one column such as Name(1):Score(*) NameScoreAdamA+AdamA-AdamBAdamC+BillD-JohnA- SELECT Name, GROUP_CONCAT(Score ORDER BY Score desc SE...

CREATE TABLE foo ( ... name CHARACTER SET utf8mb4 ... );

Vital to using character sets is to tell the MySQL-server what encoding the client's bytes are. Here is one way: SET NAMES utf8mb4; Each language (PHP, Python, Java, ...) has its own way the it usually preferable to SET NAMES. For example: SET NAMES utf8mb4, together with a column declared CH...

There are dozens of character sets with hundreds of collations. (A given collation belongs to only one character set.) See the output of SHOW COLLATION;. There are usually only 4 CHARACTER SETs that matter: ascii -- basic 7-bit codes. latin1 -- ascii, plus most characters needed for Western Eur...

Use git revert to revert existing commits, especially when those commits have been pushed to a remote repository. It records some new commits to reverse the effect of some earlier commits, which you can push safely without rewriting history. Don't use git push --force unless you wish to bring down ...

Getting zsh zsh is available on many UNIX-like platforms via their built-in package management systems. On the Debian and Ubuntu Linux distributions, zsh is available in the default package repositories and can be installed using: $ sudo apt-get install zsh # or, on newer Ubuntu distributions $ ...

You can obtain the url for an existing remote by using the command git remote get-url <name> By default, this will be git remote get-url origin

When you created your own Models in a app, they still need to be registered in order to become available in the admin pages. This is done in the admin submodule. If your app was created using manage.py startapp, an admin.py file should already lay in you app module. Otherwise create it. #myapp/a...

Javassist is a bytecode instrumentation library that allows you to modify bytecode injecting Java code that will be converted to bytecode by Javassist and added to the instrumented class/method at runtime. Lets write the first transformer that actually take an hypothetical class "com.my.to.be....

There are several packages that allow the output of data structures in form of HTML or LaTeX tables. They mostly differ in flexibility. Here I use the packages: knitr xtable pander For HTML documents --- title: "Printing Tables" author: "Martin Schmelzer" date: &quot...

C++ thrives on what is known as a Regular type (or at least Pseudo-Regular). A Regular type is a type that can be constructed and assigned-to and assigned-from via copy or move, can be destroyed, and can be compared equal-to. It can also be constructed from no arguments. Finally, it also has supp...

While a simple mock returns null (or defaults for primitives) to every call, it is possible to change that behaviour. Dependency mock = Mockito.mock(Dependency.class, new Answer() { @Override public Object answer(InvocationOnMock invocationOnMock) throws Throwable { ...