Tutorial by Examples: re

Exceptions are just regular Python objects that inherit from the built-in BaseException. A Python script can use the raise statement to interrupt execution, causing Python to print a stack trace of the call stack at that point and a representation of the exception instance. For example: >>&gt...

While reading content from a file is already asynchronous using the fs.readFile() method, sometimes we want to get the data in a Stream versus in a simple callback. This allows us to pipe this data to other locations or to process it as it comes in versus all at once at the end. const fs = require(...

You can perform redirection in Rails routes as follows: 4.0 get '/stories', to: redirect('/posts') 4.0 match "/abc" => redirect("http://example.com/abc") You can also redirect all unknown routes to a given path: 4.0 match '*path' => redirect('/'), via: :get ...

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...

Here is a full Activity class that places a Marker at the current location, and also moves the camera to the current position. There are a few thing going on in sequence here: Check Location permission Once Location permission is granted, call setMyLocationEnabled(), build the GoogleApiClient, ...

Django makes it really easy to add additional data onto requests for use within the view. For example, we can parse out the subdomain on the request's META and attach it as a separate property on the request by using middleware. class SubdomainMiddleware: def process_request(self, request): ...

Inspecting system resource usage is an efficient way to find misbehaving applications. This example is an equivalent of the traditional top command for containers: docker stats To follow the stats of specific containers, list them on the command line: docker stats 7786807d8084 7786807d8085 D...

When the last parameter of a function is a closure func loadData(id: String, completion:(result: String) -> ()) { // ... completion(result:"This is the result data") } the function can be invoked using the Trailing Closure Syntax loadData("123") { result in ...

Sometimes you want to do something with the exception you catch (like write to log or print a warning) and let it bubble up to the upper scope to be handled. To do so, you can rethrow any exception you catch: try { ... // some code here } catch (const SomeException& e) { std::cout &l...

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...

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

To download the entire repository including the full history and all branches, type: git clone <url> The example above will place it in a directory with the same name as the repository name. To download the repository and save it in a specific directory, type: git clone <url> [dire...

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)...

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...

cURL is a tool for transferring data with URL syntax. It support HTTP, FTP, SCP and many others(curl >= 7.19.4). Remember, you need to install and enable the cURL extension to use it. // a little script check is the cURL extension loaded or not if(!extension_loaded("curl")) { die...

fs.access() determines whether a path exists and what permissions a user has to the file or directory at that path. fs.access doesn't return a result rather, if it doesn't return an error, the path exists and the user has the desired permissions. The permission modes are available as a property on ...

Due to Node's asynchronous nature, creating or using a directory by first: checking for its existence with fs.stat(), then creating or using it depending of the results of the existence check, can lead to a race condition if the folder is created between the time of the check and the time of ...