Tutorial by Examples: d

Starting a File Chooser Activity public void showFileChooser() { Intent intent = new Intent(Intent.ACTION_GET_CONTENT); // Update with mime types intent.setType("*/*"); // Update with additional mime types here using a String[]. intent.putExtra(Intent.EXTRA_M...

os.mkdir('newdir') If you need to specify permissions, you can use the optional mode argument: os.mkdir('newdir', mode=0700)

Use the os.getcwd() function: print(os.getcwd())

The os module provides an interface to determine what type of operating system the code is currently running on. os.name This can return one of the following in Python 3: posix nt ce java More detailed information can be retrieved from sys.platform

Remove the directory at path: os.rmdir(path) You should not use os.remove() to remove a directory. That function is for files and using it on directories will result in an OSError

Create a DATABASE. Note that the shortened word SCHEMA can be used as a synonym. CREATE DATABASE Baseball; -- creates a database named Baseball If the database already exists, Error 1007 is returned. To get around this error, try: CREATE DATABASE IF NOT EXISTS Baseball; Similarly, DROP DATA...

A lambda closure is created when a lambda expression references the variables of an enclosing scope (global or local). The rules for doing this are the same as those for inline methods and anonymous classes. Local variables from an enclosing scope that are used within a lambda have to be final. Wit...

To improve performance one might want to add indexes to columns ALTER TABLE TABLE_NAME ADD INDEX `index_name` (`column_name`) altering to add composite (multiple column) indexes ALTER TABLE TABLE_NAME ADD INDEX `index_name` (`col1`,`col2`)

Middleware (also called pre and post hooks) are functions which are passed control during execution of asynchronous functions. Middleware is specified on the schema level and is useful for writing plugins. Mongoose 4.0 has 2 types of middleware: document middleware and query middleware. Document mid...

The AUROC is one of the most commonly used metric to evaluate a classifier's performances. This section explains how to compute it. AUC (Area Under the Curve) is used most of the time to mean AUROC, which is a bad practice as AUC is ambiguous (could be any curve) while AUROC is not. Overview – Abb...

A compound literal is an unnamed object which is created in the scope where is defined. The concept was first introduced in C99 standard. An example for compound literal is Examples from C standard, C11-§6.5.2.5/9: int *p = (int [2]){ 2, 4 }; p is initialized to the address of the first ele...

A common workflow for using Git LFS is to declare which files are intercepted through a rules-based system, just like .gitignore files. Much of time, wildcards are used to pick certain file-types to blanket track. e.g. git lfs track "*.psd" When a file matching the above pattern is adde...

7.0 OrElse Sub Main() Dim elements As List(Of Integer) = Nothing Dim average As Double = AverageElementsOrElse(elements) Console.WriteLine(average) ' Writes 0 to Console Try 'Throws ArgumentNullException average = AverageElementsOr(elements) Catch ex ...

Using the Library Database, we try to find the last book added to the database for each author. For this simple example we assume an always incrementing Id for each record added. SELECT MostRecentBook.Name, MostRecentBook.Title FROM ( SELECT Authors.Name, Books.Title, ...

As of Qt 5.1 and later you can use QQmlApplicationEngine instead of QQuickView to load and render a QML script. With QQmlApplicationEngine you do need to use a QML Window type as your root element. You can obtain the root context from the engine where you can then add global properties to the cont...

A Cython pyx file needs to be translated to C code (cythonized) and compiled before it can be used from Python. A common approach is to create an extension module which is then imported in a Python program. Code For this example we create three files: hello.pyx contains the Cython code. test.p...

class ClassWithAReallyLongName { public: class Iterator { /* ... */ }; Iterator end(); }; Defining the member end with a trailing return type: auto ClassWithAReallyLongName::end() -> Iterator { return Iterator(); } Defining the member end without a trailing return type: Clas...

>>> df ID Year Jan_salary Feb_salary Mar_salary 0 1 2016 4500 4200 4700 1 2 2016 3800 3600 4400 2 3 2016 5500 5200 5300 >>> melted_df = pd.melt(df,id_vars=['ID','Year'], v...

Create a MongoDB connection, that later you can query: $manager = new \MongoDB\Driver\Manager('mongodb://localhost:27017'); In the next example, you will learn how to query the connection object. This extension close the connection automatically, it's not necessary to close manually.

Example for searching just one user with a specific id, you should do: $options = ['limit' => 1]; $filter = ['_id' => new \MongoDB\BSON\ObjectID('578ff7c3648c940e008b457a')]; $query = new \MongoDB\Driver\Query($filter, $options); $cursor = $manager->executeQuery('database_name.collect...