Tutorial by Examples: f

To find some number (more than one) of largest or smallest values of an iterable, you can use the nlargest and nsmallest of the heapq module: import heapq # get 5 largest items from the range heapq.nlargest(5, range(10)) # Output: [9, 8, 7, 6, 5] heapq.nsmallest(5, range(10)) # Output: [...

The typical example is an abstract shape class, that can then be derived into squares, circles, and other concrete shapes. The parent class: Let's start with the polymorphic class: class Shape { public: virtual ~Shape() = default; virtual double get_surface() const = 0; virtual vo...

Packages are collections of R functions, data, and compiled code in a well-defined format. Public (and private) repositories are used to host collections of R packages. The largest collection of R packages is available from CRAN. Using CRAN A package can be installed from CRAN using following code...

To install package from local source file: install.packages(path_to_source, repos = NULL, type="source") install.packages("~/Downloads/dplyr-master.zip", repos=NULL, type="source") Here, path_to_source is absolute path of local source file. Another command that ...

Color state lists can be used as colors, but will change depending on the state of the view they are used for. To define one, create a resource file in res/color/foo.xml <?xml version="1.0" encoding="utf-8"?> <selector xmlns:android="http://schemas.android.com/ap...

A type that conforms to the SequenceType protocol can iterate through it's elements within a closure: collection.forEach { print($0) } The same could also be done with a named parameter: collection.forEach { item in print(item) } *Note: Control flow statements (such as break or continu...

You can create one table from another by adding a SELECT statement at the end of the CREATE TABLE statement: CREATE TABLE stack ( id_user INT, username VARCHAR(30), password VARCHAR(30) ); Create a table in the same database: -- create a table from another table in the same data...

A static class is lazily initialized on member access and lives for the duration of the application domain. void Main() { Console.WriteLine("Static classes are lazily initialized"); Console.WriteLine("The static constructor is only invoked when the class is first accessed&...

Variables of character type or of a derived type with length parameter may have the length parameter either assumed or deferred. The character variable name character(len=len) name is of length len throughout execution. Conversely the length specifier may be either character(len=*) ... ! Ass...

import pandas as pd import numpy as np np.random.seed(123) x = np.random.standard_normal(4) y = range(4) df = pd.DataFrame({'X':x, 'Y':y}) >>> df X Y 0 -1.085631 0 1 0.997345 1 2 0.282978 2 3 -1.506295 3

You can create a DataFrame from a list of simple tuples, and can even choose the specific elements of the tuples you want to use. Here we will create a DataFrame using all of the data in each tuple except for the last element. import pandas as pd data = [ ('p1', 't1', 1, 2), ('p1', 't2', 3, 4)...

val num = 42d Print two decimal places for num using f println(f"$num%2.2f") 42.00 Print num using scientific notation using e println(f"$num%e") 4.200000e+01 Print num in hexadecimal with a println(f"$num%a") 0x1.5p5 Other format strings can be found ...

if ([object respondsToSelector:@selector(someOptionalMethodInProtocol:)]) { [object someOptionalMethodInProtocol:argument]; }

Every authenticated user has a Firebase uid that's unique across all providers and is returned in the result of every authentication method. A good way to store your user's data is to create a node to keep all the users's data and to protect it using your security rules - Database { "use...

Oracle's CONNECT BY functionality provides many useful and nontrivial features that are not built-in when using SQL standard recursive CTEs. This example replicates these features (with a few additions for sake of completeness), using SQL Server syntax. It is most useful for Oracle developers findin...

Deleting files The unlink function deletes a single file and returns whether the operation was successful. $filename = '/path/to/file.txt'; if (file_exists($filename)) { $success = unlink($filename); if (!$success) { throw new Exception("Cannot delete $filename&qu...

for typescript 2.x: definitions from DefinitelyTyped are available via @types npm package npm i --save lodash npm i --save-dev @types/lodash but in case if you want use types from other repos then can be used old way: for typescript 1.x: Typings is an npm package that can automatically insta...

You can use the filter(_:) method on SequenceType in order to create a new array containing the elements of the sequence that satisfy a given predicate, which can be provided as a closure. For example, filtering even numbers from an [Int]: let numbers = [22, 41, 23, 30] let evenNumbers = number...

Any data structure that supports __getitem__ can have their nested structure formatted: person = {'first': 'Arthur', 'last': 'Dent'} '{p[first]} {p[last]}'.format(p=person) # 'Arthur Dent' Object attributes can be accessed using getattr(): class Person(object): first = 'Zaphod' la...

Lambda functions in C++ are syntactic sugar that provide a very concise syntax for writing functors. As such, equivalent functionality can be obtained in C++03 (albeit much more verbose) by converting the lambda function into a functor: // Some dummy types: struct T1 {int dummy;}; struct T2 {int ...