Handy Code Snippets

A bunch of code snippets that may help you ;)

What is this?

Basically a repository with handy code snippets. Not only related to programming languages, but can also be related to frameworks, technologies, etc.

Programming Languages

Java

To centralize a JFrame in the middle of the screen use this.setLocationRelativeTo(null);.

Python

Sort a list of dictionaries based on a key.

# e.g.: [{'name': 'Boyhood', 'year': 2014}, {'name': 'Citizen Kane', 'year': 1941}, {'name': 'Mad Max: Fury Road', 'year': 2015}]
# sortedList(aList, 'year')

def sortedList(aList, aKey):
  return sorted(aList, key=lambda k: k[key])

It is also possible to sort by a key of a key.

sorted(anotherList, key=lambda k: k['release_date']['year'])

R

Read a file ALL.csv and covert all the strings in the column to a comma-separated string.

names <- readLines("ALL.csv")
listOfNames <- ""
for (i in names) { listOfNames <- paste(listOfNames, "," , i) }
listOfNames <- gsub(" ", "", listOfNames)
substr(listOfNames, 2, nchar(listOfNames))

Frameworks

Flask

Use HTTPS/SSL on your web application. Don't forget to pip install flask_sslify.

from flask_sslify import SSLify

sslify = SSLify(app)

Import your app.config from a file.

app.config.from_object('<file_name>')
app.config.get('CORS_HEADERS')

Using a placeholder in your WTForms form. Don't forget to pip install wtforms.

name = StringField('Name', render_kw={"placeholder": "Your name in here"})

node.js

Use HTTPS/SSL on your web application. Don't forget to npm install express-force-https.

var secure = require('express-force-https');
var app = express();
app.use(secure);

Use an HTTP request and create a promise.

var deferred = $q.defer();

# correct: deferred.resolve(response.data);
# error: deferred.reject(err);

return deferred.promise;

pytest

Use -s option to show all prints when using pytest command.

Continuous Integration

TravisCI

• travis encrypt-file config.ini --all

  Run this command to encrypt the file config.ini and add the reference to .travis.yml.

Text Editors

vim

Notable commands:

• :q to close the file. Use ! to force quit.
• :w to save your file.
• /<word> to search for a <word>, if you want to keep searching, type /.
• dd to delete a line.
• i to enter INSERT mode.
• esc to leave the INSERT mode.
• v to select the text (or V to select the whole line).
• d to cut, y to copy and P to paste.

Operating Systems

Linux

• Check your systems specs on your Terminal: lshw. Use --short to show a short version.

Unix

These commands are valid for Linux and macOS.

• tail -f foo.log to keep the file opened and showing the last updates on your file. Very useful for system logs.
• touch to create a new file.
• mkdir to create a new directory.
• pwd to show the current path.
• whoami to show the current logged user.

macOS

• say <something> and your Mac will say <something> to you.