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Django Migrations without Downtime

The following instructions describe a set of processes allowing you to run Django database migrations against a production database without having to bring the web service down.

Note that in the below instructions, migrations are all run manually at explicit points, and are not an automatic part of the deployment process.

Adding Fields or Tables

Adding a (nullable) field or a new table

1. Make the model or column addition in your code.

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# extracted from http//www.naturalearthdata.com/download/110m/cultural/ne_110m_admin_0_countries.zip
# under public domain terms

country_bounding_boxes = {
    'AF': ('Afghanistan', (60.5284298033, 29.318572496, 75.1580277851, 38.4862816432)),
    'AO': ('Angola', (11.6400960629, -17.9306364885, 24.0799052263, -4.43802336998)),
    'AL': ('Albania', (19.3044861183, 39.624997667, 21.0200403175, 42.6882473822)),
    'AE': ('United Arab Emirates', (51.5795186705, 22.4969475367, 56.3968473651, 26.055464179)),
    'AR': ('Argentina', (-73.4154357571, -55.25, -53.628348965, -21.8323104794)),
    'AM': ('Armenia', (43.5827458026, 38.7412014837, 46.5057198423, 41.2481285671)),

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/** Determines if an object is freed
@param obj is the object of interest
@param freeFn is a function that frees the object.
@returns a promise that resolves to {freed: boolean, memoryDiff:number}

@author Steve Hanov <steve.hanov@gmail.com>
*/
function isObjectFreed(obj, freeFn) {
  return new Promise( (resolve) => {
    if (!performance.memory) {

dmarchuk

import django_filters


class CommaSeparatedValueFilter(django_filters.CharFilter):
    """Accept comma separated string as value and convert it to list.

    It's useful for __in lookups.
    """

    def filter(self, qs, value):

dmarchuk

# JS
find . -name '*.js' | xargs wc -l | sort -nr

# SCSS
find . -name '*.scss' | xargs wc -l | sort -nr

dmarchuk

BEMIT Cheatsheet

Give developers more knowledge about how the classes behave in a non-relative sense: BEM + ITCSS = BEMIT

• More Transparent UI Code with Namespaces
• BEMIT: Taking the BEM Naming Convention a Step Further

Evolution

BEM:

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#!/bin/bash

for i in `seq 1 50`;
do
   rg -F id=$i\).price;
done

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Grep string in logs

docker logs nginx 2>&1 | grep "127."

Create file from logs

docker logs nginx > stdout.log 2>stderr.log

Mac - clean docker orphaned volumes

docker volume rm $(docker volume ls -qf dangling=true)

dmarchuk

import csv
import requests

result = ''

for i in range(195):
    list_json = requests.get(url, headers={
        'X-Requested-With': 'XMLHttpRequest',
        'User-Agent': 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13_1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/65.0.3325.181 Safari/537.36',
        'Accept': '*/*',

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/**
 * Override default 'renderItems()' function of selectivity
 * to accept option with value='' (empty string, item.id === '') as a valid option.
 *
 * @param items Array of result items.
 * @returns HTML-formatted string to display the result items.
 */
$.Selectivity.Dropdown.prototype.renderItems = function (items) {
    const selectivity = this.selectivity;
    const originalEl = selectivity.options.element;