Tutorial by Examples: ga

Creating a figure

The figure contains all the plot elements. The main way to create a figure in matplotlib is to use pyplot. import matplotlib.pyplot as plt fig = plt.figure() You can optionally supply a number, which you can use to access a previously-created figure. If a number is not supplied, the last-create...

POM Aggregation

The modules of a multi-module project are aggregated from a hierarchical structure. The root pom packing should look like: <packaging>pom</packaging> The following will be the directory structure of the project: |-- sample-app \ `-- pom.xml |-- sample-module-1 | `--...

Customizing a matplotlib plot

import pylab as plt import numpy as np plt.style.use('ggplot') fig = plt.figure(1) ax = plt.gca() # make some testing data x = np.linspace( 0, np.pi, 1000 ) test_f = lambda x: np.sin(x)*3 + np.cos(2*x) # plot the test data ax.plot( x, test_f(x) , lw = 2) # set the axis labels ax...

Create new Ring application with http-kit

Ring is de-facto standard API for clojure HTTP applications, similar to Ruby's Rack and Python's WSGI. We're going to use it with http-kit webserver. Create new Leiningen project: lein new app myapp Add http-kit dependency to project.clj: :dependencies [[org.clojure/clojure "1.8.0&quot...

Using a predicate as a spec

Any predicate function can be used as a spec. Here's a simple example: (clojure.spec/valid? odd? 1) ;;=> true (clojure.spec/valid? odd? 2) ;;=> false the valid? function will take a spec and a value and return true if the value conforms to the spec and false otherwise. One other inte...

fdef: writing a spec for a function

Let's say we have the following function: (defn nat-num-count [nums] (count (remove neg? nums))) We can write a spec for this function by defining a function spec of the same name: (clojure.spec/fdef nat-num-count :args (s/cat :nums (s/coll-of number?)) :ret integer? ...

Controlling Access to or from a Route

The default Angular router allows navigation to and from any route unconditionally. This is not always the desired behavior. In a scenario where a user may conditionally be allowed to navigate to or from a route, a Route Guard may be used to restrict this behavior. If your scenario fits one of the...

Delegated Events

Let's start with example. Here is a very simple example HTML. Example HTML <html> <head> </head> <body> <ul> <li> <a href="some_url/">Link 1</a> </li> &l...

Creating a UIColor from hexadecimal number or string

You can create a UIColor from a hexadecimal number or string, e.g. 0xff00cc, "#FFFFFF" Swift Int Value extension UIColor { convenience init(hex: Int, alpha: CGFloat = 1.0) { let r = CGFloat((hex >> 16) & 0xff) / 255 let g = CGFloat((hex >> 08) &amp...
iOS • UIColor

Validating A Number Is A Float

Validates value as float, and converts to float on success. var_dump(filter_var(1, FILTER_VALIDATE_FLOAT)); var_dump(filter_var(1.0, FILTER_VALIDATE_FLOAT)); var_dump(filter_var(1.0000, FILTER_VALIDATE_FLOAT)); var_dump(filter_var(1.00001, FILTER_VALIDATE_FLOAT)); var_dump(filter_var('1', FILTE...

Uploading a file via Multipart

Declare your interface with Retrofit2 annotations: public interface BackendApiClient { @Multipart @POST("/uploadFile") Call<RestApiDefaultResponse> uploadPhoto(@Part("file\"; filename=\"photo.jpg\" ") RequestBody photo); } Where RestApiDef...

Promisifying a callback

Callback-based: db.notification.email.find({subject: 'promisify callback'}, (error, result) => { if (error) { console.log(error); } // normal code here }); This uses bluebird's promisifyAll method to promisify what is conventionally callback-based code like above. blueb...

Synthesising audio

In this example we show how to generate a simple sine wave, and output it on the user's speakers/headphones. let audioContext = new (window.AudioContext || window.webkitAudioContext)(); let sourceNode = audioContext.createOscillator(); sourceNode.type = 'sine'; sourceNode.frequency.value = 261...

Checking, setting, clearing, and toggling individual bits. Using long as bit mask

Assuming we want to modify bit n of an integer primitive, i (byte, short, char, int, or long): (i & 1 << n) != 0 // checks bit 'n' i |= 1 << n; // sets bit 'n' to 1 i &= ~(1 << n); // sets bit 'n' to 0 i ^= 1 << n; // toggles the value of bit 'n' Us...

Creating and Initializing Image Objects with file contents

Creating and returning an image object by loading the image data from the file at the specified path. Example: UIImage *image = [UIImage imageWithContentsOfFile:[[NSBundle mainBundle] pathForResource:[cellCountry objectForKey:@"Country_Flag"] ofType:nil]]; Using Array: Example NSM...
iOS • UIImage

Passing arguments by reference or value

In JavaScript all arguments are passed by value. When a function assigns a new value to an argument variable, that change will not be visible to the caller: var obj = {a: 2}; function myfunc(arg){ arg = {a: 5}; // Note the assignment is to the parameter variable itself } myfunc(obj); conso...

Getting a shell into a running (detached) container

Log into a running container A user can enter a running container in a new interactive bash shell with exec command. Say a container is called jovial_morse then you can get an interactive, pseudo-TTY bash shell by running: docker exec -it jovial_morse bash Log into a running container with a s...

Using an extension method for collection initialization

Collection initialization syntax can be used when instantiating any class which implements IEnumerable and has a method named Add which takes a single parameter. In previous versions, this Add method had to be an instance method on the class being initialized. In C#6, it can also be an extension me...

Using anonymous structs for decoding

The goal with using anonymous structs is to decode only the information we care about without littering our app with types that are used only in a single function. jsonBlob := []byte(` { "_total": 1, "_links": { "self": "https://api.twitch.tv/k...
Go • JSON

Referencing a class

To obtain a reference to a KClass object representing some class use double colons: val c1 = String::class val c2 = MyClass::class

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