PyCon Italia 2019
Internet delle cose con Redis e django-channels
Development of vertical software solutions for medium to large businesses
Intranet, extranet, web services and IOT
Focused on technologies such as Python, Django, Redis, WebSockets, HTMX, IoT.
Real-time data acquisition, from Arduino to the web, using PubSub with Redis, Django and other friends
A Django app which provides advanced integration for a Django project with the jQuery Javascript library DataTables.net, when used in server-side processing mode.
Demo site
A Django helper app to add editing capabilities to the frontend using modal forms.
Demo site
A Django app to run new background tasks from either admin or cron, and inspect task history from admin; based on django-rq
A collection of tools to trace, analyze and render Querysets
Helper used to remove oldest records from specific db tables in a Django project
Example of a simple C# console application that prints "Hello, World!" to the console using top-level statements:
dotnet new console -n HelloWorldApp cd HelloWorldApp cat Program.cs // Program.cs using System; Console.WriteLine("Hello, World!"); dotnet run
Example of a simple C# console application that prints "Hello, World!" to the console using top-level statements:
dotnet new console -n HelloWorldApp cd HelloWorldApp cat Program.cs // Program.cs using System; Console.WriteLine("Hello, World!"); dotnet run
Quick and easy:
fetch('https://reqbin.com/echo/get/json', { method: 'GET', headers: { 'Accept': 'application/json', }, }) .then(response => response.json()) .then(response => console.log(JSON.stringify(response)))
The following is more elaborated with the purpose to collect all errors is a single catch handler:
In the latter case, the response might contain further details JSON-serialized and we want to inspect them
fetch( '/backend/j/mto_evaluate_final_stock_total', { method: "post", body: data, mode: 'cors', // 'no-cors', cache: 'no-cache', credentials: 'same-origin', headers: { // make sure request.is_ajax() return True on the server 'X-Requested-With': 'XMLHttpRequest', 'X-CSRFToken': getCookie('csrftoken') } } ) .then(function(response) { if (response.ok) { return response.json() } // if not 200-OK, reject instead of throw // Here, the plan is to get {status: 4XX, message: 'a message'} format as a result in both cases. // See: https://stackoverflow.com/questions/38235715/fetch-reject-promise-and-catch-the-error-if-status-is-not-ok#67660773 return Promise.reject(response) }) .then(function(data) { console.log(data) ... use data ... }) .catch(function(error) { // Show error console.error(error.status, error.statusText); // also get error messages, if any // Again, see: https://stackoverflow.com/questions/38235715/fetch-reject-promise-and-catch-the-error-if-status-is-not-ok#67660773 error.json().then(function(json) { console.error(json); }) }) .finally(function() { })
// bind to the form’s submit event form.addEventListener('submit', function(event) { // prevent the form from performing its default submit action event.preventDefault(); header.classList.add('loading'); // serialize the form’s content and send via an AJAX call // using the form’s defined method and action let url = form.getAttribute('action') || self.options.url; let method = form.getAttribute('method') || 'post'; // We use FormData // to allow files upload (i.e. process <input type="file"> as expected) // Note that, using FormData, we also need (with jQuery): // - processData: false // - contentType: false let data = new FormData(form); //console.log('form data: %o', new URLSearchParams(data).toString()); self._notify('submitting', {method: method, url: url, data:data}); let promise = fetch( self.options.url, { method: "post", body: data, mode: 'cors', // 'no-cors', cache: 'no-cache', credentials: 'same-origin', headers: { // make sure request.is_ajax() return True on the server 'X-Requested-With': 'XMLHttpRequest', 'X-CSRFToken': getCookie('csrftoken') } } ); promise.then(response => { if (response.ok) { // Upon receiving a JSON response, we assume that the form has been validated, // so we can close the modal if (response.headers.get('Content-Type') === 'application/json') { response.json().then(data => { self._notify('submitted', {method: method, url: url, data: data}); self.close(); }) .catch(error => { FrontendForms.display_server_error(error); }) } else { response.text().then(data => { // update the modal body with the new form body.innerHTML = data; // Does the response contain a form ? let form = self.element.querySelector('.dialog-content .dialog-body form'); if (form !== null) { // If the server sends back a successful response, // we need to further check the HTML received // If xhr contains any field errors, // the form did not validate successfully, // so we keep it open for further editing //if (jQuery(xhr).find('.has-error').length > 0) { if (form.querySelectorAll('.has-error').length > 0 || form.querySelectorAll('.errorlist').length > 0) { self._notify('loaded', {url: url}); self._form_ajax_submit(true); } else { // otherwise, we've done and can close the modal self._notify('submitted', {method: method, url: url, data: data}); self.close(); } } // If not, assume we received a feedback for the user after successfull submission, so: // - keep the dialog open // - hide the save button else { // We also notify the user about successful submission self._notify('submitted', {method: method, url: url, data: data}); btn_save.style.display = 'none'; } }); } } else { self._notify('submission_failure', {method: method, url: url, data: data, error: response.statusText}); FrontendForms.display_server_error(response.statusText); } }).catch(error => { self._notify('submission_failure', {method: method, url: url, data: data, error:error}); FrontendForms.display_server_error(error.toString()); }).finally(() => { header.classList.remove('loading'); });
where:
function getCookie(name) { var value = '; ' + document.cookie, parts = value.split('; ' + name + '='); if (parts.length == 2) return parts.pop().split(';').shift(); }
Quick and easy:
fetch('https://reqbin.com/echo/get/json', { method: 'GET', headers: { 'Accept': 'application/json', }, }) .then(response => response.json()) .then(response => console.log(JSON.stringify(response)))
The following is more elaborated with the purpose to collect all errors is a single catch handler:
In the latter case, the response might contain further details JSON-serialized and we want to inspect them
fetch( '/backend/j/mto_evaluate_final_stock_total', { method: "post", body: data, mode: 'cors', // 'no-cors', cache: 'no-cache', credentials: 'same-origin', headers: { // make sure request.is_ajax() return True on the server 'X-Requested-With': 'XMLHttpRequest', 'X-CSRFToken': getCookie('csrftoken') } } ) .then(function(response) { if (response.ok) { return response.json() } // if not 200-OK, reject instead of throw // Here, the plan is to get {status: 4XX, message: 'a message'} format as a result in both cases. // See: https://stackoverflow.com/questions/38235715/fetch-reject-promise-and-catch-the-error-if-status-is-not-ok#67660773 return Promise.reject(response) }) .then(function(data) { console.log(data) ... use data ... }) .catch(function(error) { // Show error console.error(error.status, error.statusText); // also get error messages, if any // Again, see: https://stackoverflow.com/questions/38235715/fetch-reject-promise-and-catch-the-error-if-status-is-not-ok#67660773 error.json().then(function(json) { console.error(json); }) }) .finally(function() { })
// bind to the form’s submit event form.addEventListener('submit', function(event) { // prevent the form from performing its default submit action event.preventDefault(); header.classList.add('loading'); // serialize the form’s content and send via an AJAX call // using the form’s defined method and action let url = form.getAttribute('action') || self.options.url; let method = form.getAttribute('method') || 'post'; // We use FormData // to allow files upload (i.e. process <input type="file"> as expected) // Note that, using FormData, we also need (with jQuery): // - processData: false // - contentType: false let data = new FormData(form); //console.log('form data: %o', new URLSearchParams(data).toString()); self._notify('submitting', {method: method, url: url, data:data}); let promise = fetch( self.options.url, { method: "post", body: data, mode: 'cors', // 'no-cors', cache: 'no-cache', credentials: 'same-origin', headers: { // make sure request.is_ajax() return True on the server 'X-Requested-With': 'XMLHttpRequest', 'X-CSRFToken': getCookie('csrftoken') } } ); promise.then(response => { if (response.ok) { // Upon receiving a JSON response, we assume that the form has been validated, // so we can close the modal if (response.headers.get('Content-Type') === 'application/json') { response.json().then(data => { self._notify('submitted', {method: method, url: url, data: data}); self.close(); }) .catch(error => { FrontendForms.display_server_error(error); }) } else { response.text().then(data => { // update the modal body with the new form body.innerHTML = data; // Does the response contain a form ? let form = self.element.querySelector('.dialog-content .dialog-body form'); if (form !== null) { // If the server sends back a successful response, // we need to further check the HTML received // If xhr contains any field errors, // the form did not validate successfully, // so we keep it open for further editing //if (jQuery(xhr).find('.has-error').length > 0) { if (form.querySelectorAll('.has-error').length > 0 || form.querySelectorAll('.errorlist').length > 0) { self._notify('loaded', {url: url}); self._form_ajax_submit(true); } else { // otherwise, we've done and can close the modal self._notify('submitted', {method: method, url: url, data: data}); self.close(); } } // If not, assume we received a feedback for the user after successfull submission, so: // - keep the dialog open // - hide the save button else { // We also notify the user about successful submission self._notify('submitted', {method: method, url: url, data: data}); btn_save.style.display = 'none'; } }); } } else { self._notify('submission_failure', {method: method, url: url, data: data, error: response.statusText}); FrontendForms.display_server_error(response.statusText); } }).catch(error => { self._notify('submission_failure', {method: method, url: url, data: data, error:error}); FrontendForms.display_server_error(error.toString()); }).finally(() => { header.classList.remove('loading'); });
where:
function getCookie(name) { var value = '; ' + document.cookie, parts = value.split('; ' + name + '='); if (parts.length == 2) return parts.pop().split(';').shift(); }
sudo dd if=/dev/zero of=testfile bs=1G count=1 oflag=dsync && sudo rm testfile
sudo dd if=/dev/zero of=testfile bs=1G count=1 oflag=dsync && sudo rm testfile
#!/usr/bin/env python3 import pprint import json import gitlab import argparse # Requirements # python-gitlab==4.11.1 GITLAB_URL = "https://gitlab.brainstorm.it" GITLAB_PRIVATE_TOKEN = "glpat-******************" GITLAB_PROJECT = 77 PAGE_BREAK_STRING = '<div style="page-break-after: always;"></div>' class GitlabClient(gitlab.Gitlab): def __init__(self, project_id): super().__init__(GITLAB_URL, GITLAB_PRIVATE_TOKEN, order_by='created_at') self.project = self.projects.get(project_id) def retrieve_issue(self, issue_id): issue = self.project.issues.get(issue_id) base_url = issue.web_url # Es: 'https://gitlab.brainstorm.it/group/project/-/issues/36' position = base_url.find('/-/') if position >= 0: base_url = base_url[:position] # Es: 'https://gitlab.brainstorm.it/group/project' data = json.loads(issue.to_json()) self.fix_image_links(data, base_url) data['notes'] = [] notes = issue.notes.list(all=True) notes = sorted([n for n in notes if not n.system], key=lambda k: k.created_at) for n in notes: note = json.loads(n.to_json()) self.fix_image_links(note, base_url) data['notes'].append(note) return data def fix_image_links(self, data, base_url): text = data.get('description', data.get('body')) text = text.replace('/uploads/', base_url+'/uploads/') if 'description' in data: data['description'] = text else: data['body'] = text def to_markdown(data): text = "" for k, v in data.items(): text += '\n# [%d] %s\n\n' % (k, v['title']) text += "### %s (%s)\n\n" % (v['author']['name'], v['created_at']) text += "**Link**: %s\n\n" % v['web_url'] text += v['description'] text += "\n\n" for n in v['notes']: text += "\n\n" + (80*'-') + "\n\n" text += "### %s (%s)\n\n" % (n['author']['name'], v['created_at']) text += n['body'] text += "\n\n" text += "\n\n" + PAGE_BREAK_STRING return text def main(): parser = argparse.ArgumentParser(description="...") parser.add_argument('issue_ids', nargs="+", type=int) parser.add_argument("--project_id", "-p", type=int, default=GITLAB_PROJECT, help="Default: %d" % GITLAB_PROJECT) parser.add_argument("--format", type=str, choices=["", "markdown", ], default="") args = parser.parse_args() project_id = args.project_id client = GitlabClient(GITLAB_PROJECT) data = {} for issue_id in args.issue_ids: issue_data = client.retrieve_issue(issue_id) data[issue_id] = issue_data if args.format == 'markdown': print(to_markdown(data)) else: pprint.pprint(data) if __name__ == '__main__': main()
#!/usr/bin/env python3 import pprint import json import gitlab import argparse # Requirements # python-gitlab==4.11.1 GITLAB_URL = "https://gitlab.brainstorm.it" GITLAB_PRIVATE_TOKEN = "glpat-******************" GITLAB_PROJECT = 77 PAGE_BREAK_STRING = '<div style="page-break-after: always;"></div>' class GitlabClient(gitlab.Gitlab): def __init__(self, project_id): super().__init__(GITLAB_URL, GITLAB_PRIVATE_TOKEN, order_by='created_at') self.project = self.projects.get(project_id) def retrieve_issue(self, issue_id): issue = self.project.issues.get(issue_id) base_url = issue.web_url # Es: 'https://gitlab.brainstorm.it/group/project/-/issues/36' position = base_url.find('/-/') if position >= 0: base_url = base_url[:position] # Es: 'https://gitlab.brainstorm.it/group/project' data = json.loads(issue.to_json()) self.fix_image_links(data, base_url) data['notes'] = [] notes = issue.notes.list(all=True) notes = sorted([n for n in notes if not n.system], key=lambda k: k.created_at) for n in notes: note = json.loads(n.to_json()) self.fix_image_links(note, base_url) data['notes'].append(note) return data def fix_image_links(self, data, base_url): text = data.get('description', data.get('body')) text = text.replace('/uploads/', base_url+'/uploads/') if 'description' in data: data['description'] = text else: data['body'] = text def to_markdown(data): text = "" for k, v in data.items(): text += '\n# [%d] %s\n\n' % (k, v['title']) text += "### %s (%s)\n\n" % (v['author']['name'], v['created_at']) text += "**Link**: %s\n\n" % v['web_url'] text += v['description'] text += "\n\n" for n in v['notes']: text += "\n\n" + (80*'-') + "\n\n" text += "### %s (%s)\n\n" % (n['author']['name'], v['created_at']) text += n['body'] text += "\n\n" text += "\n\n" + PAGE_BREAK_STRING return text def main(): parser = argparse.ArgumentParser(description="...") parser.add_argument('issue_ids', nargs="+", type=int) parser.add_argument("--project_id", "-p", type=int, default=GITLAB_PROJECT, help="Default: %d" % GITLAB_PROJECT) parser.add_argument("--format", type=str, choices=["", "markdown", ], default="") args = parser.parse_args() project_id = args.project_id client = GitlabClient(GITLAB_PROJECT) data = {} for issue_id in args.issue_ids: issue_data = client.retrieve_issue(issue_id) data[issue_id] = issue_data if args.format == 'markdown': print(to_markdown(data)) else: pprint.pprint(data) if __name__ == '__main__': main()
Adapted from:
"Django: Basic Auth for one view (avoid middleware)"
file decorators.py:
import base64 from django.http import HttpResponse from django.contrib.auth import authenticate def basicauth(view): """ Adapted from: "Django: Basic Auth for one view (avoid middleware)" https://stackoverflow.com/questions/46426683/django-basic-auth-for-one-view-avoid-middleware#47902577 """ def wrap(request, *args, **kwargs): if 'HTTP_AUTHORIZATION' in request.META: auth = request.META['HTTP_AUTHORIZATION'].split() if len(auth) == 2: if auth[0].lower() == "basic": uname, passwd = base64.b64decode(auth[1]).decode( "utf8" ).split(':', 1) user = authenticate(username=uname, password=passwd) if user is not None and user.is_active: request.user = user return view(request, *args, **kwargs) response = HttpResponse() response.status_code = 401 response['WWW-Authenticate'] = 'Basic realm="{}"'.format( #settings.BASIC_AUTH_REALM 'api' ) return response return wrap
file view.py:
from django.http import JsonResponse from .decorators import basicauth @basicauth def get_data(request, query_name): try: if not request.user.is_authenticated: raise Exception("Authentication required") ... data = { whatever } response = JsonResponse( { "success": True, "data": data, } ) except Exception as e: response = JsonResponse( { "success": False, "errors": [ { "status": 400, "source": { "view": "get_dw_data()", "traceback": traceback.format_exc() if config.EXCHANGE_API_TRACEBACK else "", }, "title": "Error", "detail": str(e), } ], }, safe=True, status=400, ) return response
Adapted from:
"Django: Basic Auth for one view (avoid middleware)"
file decorators.py:
import base64 from django.http import HttpResponse from django.contrib.auth import authenticate def basicauth(view): """ Adapted from: "Django: Basic Auth for one view (avoid middleware)" https://stackoverflow.com/questions/46426683/django-basic-auth-for-one-view-avoid-middleware#47902577 """ def wrap(request, *args, **kwargs): if 'HTTP_AUTHORIZATION' in request.META: auth = request.META['HTTP_AUTHORIZATION'].split() if len(auth) == 2: if auth[0].lower() == "basic": uname, passwd = base64.b64decode(auth[1]).decode( "utf8" ).split(':', 1) user = authenticate(username=uname, password=passwd) if user is not None and user.is_active: request.user = user return view(request, *args, **kwargs) response = HttpResponse() response.status_code = 401 response['WWW-Authenticate'] = 'Basic realm="{}"'.format( #settings.BASIC_AUTH_REALM 'api' ) return response return wrap
file view.py:
from django.http import JsonResponse from .decorators import basicauth @basicauth def get_data(request, query_name): try: if not request.user.is_authenticated: raise Exception("Authentication required") ... data = { whatever } response = JsonResponse( { "success": True, "data": data, } ) except Exception as e: response = JsonResponse( { "success": False, "errors": [ { "status": 400, "source": { "view": "get_dw_data()", "traceback": traceback.format_exc() if config.EXCHANGE_API_TRACEBACK else "", }, "title": "Error", "detail": str(e), } ], }, safe=True, status=400, ) return response
from ninja import Router v1_router = Router(tags=["cclib"]) @v1_router.get("/hello") def hello(request): return "Hello world!"
from typing import List import uuid from django.shortcuts import get_object_or_404 from ninja import Router from ninja import Schema, ModelSchema from ninja.security import django_auth from cclib.resources.models import Document v1_router = Router(tags=["cclib"]) class DocumentSchema(ModelSchema): class Meta: model = Document fields = "__all__" @v1_router.get("/documents/{uuid:document_id}", response=DocumentSchema, auth=django_auth) def get_document(request, document_id: uuid.UUID): return get_object_or_404(Document, pk=document_id) @v1_router.get("/documents", response=List[DocumentSchema], auth=django_auth) def list_documents(request): qs = Document.objects.all() return qs
There is also often a need to return responses with some nested/child objects ...
https://django-ninja.dev/guides/response/#nested-objects
See also:
Example:
import traceback from typing import List from ninja import Router from ninja import Schema, ModelSchema from ninja.errors import HttpError from ninja.security import django_auth from ninja.security import django_auth_superuser from django.conf import settings from django.contrib.auth.models import Group from django.contrib.auth import get_user_model v1_router = Router(tags=["ccserver"]) class GroupSchema(ModelSchema): class Meta: model = Group fields = "__all__" class UserSchema(ModelSchema): # See: "Nested objects" # https://django-ninja.dev/guides/response/#nested-objects groups: List[GroupSchema] = [] class Meta: model = get_user_model() #fields = "__all__" fields = [ 'id', 'username', ] @v1_router.get("/users", response=List[UserSchema], auth=django_auth_superuser) def list_users(request): try: User = get_user_model() qs = User.objects.all() except Exception as e: # See: "Throwing HTTP responses with exceptions" # https://django-ninja.dev/guides/errors/#throwing-http-responses-with-exceptions raise HttpError(500, str(e) + "\n" + traceback.format_exc()) return qs
Instead of a nested response, you may want to just flatten the response output.
The Ninja Schema object extends Pydantic's Field(..., alias="") format to work with dotted responses.
https://django-ninja.dev/guides/authentication/
Examples:
from ninja import NinjaAPI from ninja.security import django_auth api = NinjaAPI(csrf=True) @api.get("/pets", auth=django_auth) def pets(request): return f"Authenticated user {request.auth}"
If you need to authorize only a superuser, you can use from ninja.security import django_auth_superuser instead.
Here's an example where the client, in order to authenticate, needs to pass a header:
Authorization: Bearer supersecret:
from ninja.security import HttpBearer class AuthBearer(HttpBearer): def authenticate(self, request, token): if token == "supersecret": return token @api.get("/bearer", auth=AuthBearer()) def bearer(request): return {"token": request.auth}
As an alternative to custom exceptions and writing handlers for it - you can as well throw http exception that will lead to returning a http response with desired code
https://django-ninja.dev/guides/errors/#throwing-http-responses-with-exceptions
from ninja.errors import HttpError @api.get("/some/resource") def some_operation(request): if True: raise HttpError(503, "Service Unavailable. Please retry later.")
Have separate routers for each domain:
https://django-ninja.dev/guides/routers/
See also the following discussion:
https://www.reddit.com/r/django/comments/13zg8uw/django_ninja_architecture/
from ninja import Router v1_router = Router(tags=["cclib"]) @v1_router.get("/hello") def hello(request): return "Hello world!"
from typing import List import uuid from django.shortcuts import get_object_or_404 from ninja import Router from ninja import Schema, ModelSchema from ninja.security import django_auth from cclib.resources.models import Document v1_router = Router(tags=["cclib"]) class DocumentSchema(ModelSchema): class Meta: model = Document fields = "__all__" @v1_router.get("/documents/{uuid:document_id}", response=DocumentSchema, auth=django_auth) def get_document(request, document_id: uuid.UUID): return get_object_or_404(Document, pk=document_id) @v1_router.get("/documents", response=List[DocumentSchema], auth=django_auth) def list_documents(request): qs = Document.objects.all() return qs
There is also often a need to return responses with some nested/child objects ...
https://django-ninja.dev/guides/response/#nested-objects
See also:
Example:
import traceback from typing import List from ninja import Router from ninja import Schema, ModelSchema from ninja.errors import HttpError from ninja.security import django_auth from ninja.security import django_auth_superuser from django.conf import settings from django.contrib.auth.models import Group from django.contrib.auth import get_user_model v1_router = Router(tags=["ccserver"]) class GroupSchema(ModelSchema): class Meta: model = Group fields = "__all__" class UserSchema(ModelSchema): # See: "Nested objects" # https://django-ninja.dev/guides/response/#nested-objects groups: List[GroupSchema] = [] class Meta: model = get_user_model() #fields = "__all__" fields = [ 'id', 'username', ] @v1_router.get("/users", response=List[UserSchema], auth=django_auth_superuser) def list_users(request): try: User = get_user_model() qs = User.objects.all() except Exception as e: # See: "Throwing HTTP responses with exceptions" # https://django-ninja.dev/guides/errors/#throwing-http-responses-with-exceptions raise HttpError(500, str(e) + "\n" + traceback.format_exc()) return qs
Instead of a nested response, you may want to just flatten the response output.
The Ninja Schema object extends Pydantic's Field(..., alias="") format to work with dotted responses.
https://django-ninja.dev/guides/authentication/
Examples:
from ninja import NinjaAPI from ninja.security import django_auth api = NinjaAPI(csrf=True) @api.get("/pets", auth=django_auth) def pets(request): return f"Authenticated user {request.auth}"
If you need to authorize only a superuser, you can use from ninja.security import django_auth_superuser instead.
Here's an example where the client, in order to authenticate, needs to pass a header:
Authorization: Bearer supersecret:
from ninja.security import HttpBearer class AuthBearer(HttpBearer): def authenticate(self, request, token): if token == "supersecret": return token @api.get("/bearer", auth=AuthBearer()) def bearer(request): return {"token": request.auth}
As an alternative to custom exceptions and writing handlers for it - you can as well throw http exception that will lead to returning a http response with desired code
https://django-ninja.dev/guides/errors/#throwing-http-responses-with-exceptions
from ninja.errors import HttpError @api.get("/some/resource") def some_operation(request): if True: raise HttpError(503, "Service Unavailable. Please retry later.")
Have separate routers for each domain:
https://django-ninja.dev/guides/routers/
See also the following discussion:
https://www.reddit.com/r/django/comments/13zg8uw/django_ninja_architecture/
.
Strategy:
function print(text) { element.textContent = text } function returnValueAfterDelay(value, delay) { let promise = new Promise(function(resolve, reject) { function callback() { resolve(value) } setTimeout(callback, delay); }) return promise } function main() { returnValueAfterDelay(123, 1000).then( function(value) { print(value) } ) } main()
or the similar version using "arrow functions" instead of "regular functions" ... (but does anyone really think it is more readable?) ...
print = (text) => { element.textContent = text } let returnValueAfterDelay = (value, delay) => { let promise = new Promise((resolve, reject) => { let callback = () => resolve(value) setTimeout(callback, delay) }) return promise } let main = () => { returnValueAfterDelay(123, 1000).then( (value) => print(value) ) } main()
However:
It is recommended to use regular functions when dealing with Promises, Callback functions with dynamic context, and Object methods.
.
Strategy:
function print(text) { element.textContent = text } function returnValueAfterDelay(value, delay) { let promise = new Promise(function(resolve, reject) { function callback() { resolve(value) } setTimeout(callback, delay); }) return promise } function main() { returnValueAfterDelay(123, 1000).then( function(value) { print(value) } ) } main()
or the similar version using "arrow functions" instead of "regular functions" ... (but does anyone really think it is more readable?) ...
print = (text) => { element.textContent = text } let returnValueAfterDelay = (value, delay) => { let promise = new Promise((resolve, reject) => { let callback = () => resolve(value) setTimeout(callback, delay) }) return promise } let main = () => { returnValueAfterDelay(123, 1000).then( (value) => print(value) ) } main()
However:
It is recommended to use regular functions when dealing with Promises, Callback functions with dynamic context, and Object methods.
file main/middleware.py
import logging from django.utils.deprecation import MiddlewareMixin from django.conf import settings logging.basicConfig(level=logging.INFO, format="%(asctime)s:%(levelname)s:%(message)s") def to_string(value): text = str(value) nmax = settings.LOG_REQUEST_DETAIL_MAX_LENGTH if nmax > 0 and len(text) > nmax: text = text[:nmax] + "......" return text def user_ip_address(request): x_forwarded_for = request.META.get('HTTP_X_FORWARDED_FOR', None) if x_forwarded_for: remote_address = x_forwarded_for.split(',')[0].strip() else: remote_address = request.META.get('REMOTE_ADDR', None) return remote_address class LoggingMiddleware(MiddlewareMixin): """ Log requests and responses Adapted from: https://scripting4ever.wordpress.com/2020/07/27/how-to-log-the-request-and-response-via-django-middleware/ """ def process_request(self, request): if settings.LOG_REQUEST_DETAILS: logging.info("=" * 80) logging.info( "Request Method: " + to_string(request.META.get("REQUEST_METHOD", "???")) ) logging.info("URL requested: " + to_string(request.path)) logging.info("Request Body Contents: " + to_string(request.body)) logging.info("Request Headers: " + to_string(request.headers)) logging.info( "Content Length: " + to_string(request.META.get("CONTENT_LENGTH", "???")) ) logging.info( #"Client IP Address: " + to_string(request.META.get("REMOTE_ADDR", "???")) "Client IP Address: " + to_string(user_ip_address(request)) ) logging.info( "Host Name of Client: " + to_string(request.META.get("REMOTE_HOST", "???")) ) logging.info( "Host Name or Server: " + to_string(request.META.get("SERVER_NAME", "???")) ) logging.info( "Port of the Server: " + to_string(request.META.get("SERVER_PORT", "???")) ) logging.info("-" * 80) return None def process_response(self, request, response): if settings.LOG_REQUEST_DETAILS: logging.info("Response Content: " + to_string(response.content)) logging.info("Response Code: " + to_string(response.status_code)) logging.info("Response Headers: " + to_string(response.headers)) logging.info("=" * 80) return response
then, in settings.py:
MIDDLEWARE = [ ... 'main.middleware.LoggingMiddleware', ] ... LOG_REQUEST_DETAILS = True LOG_REQUEST_DETAIL_MAX_LENGTH = 200
Adapted from:
file main/middleware.py
import logging from django.utils.deprecation import MiddlewareMixin from django.conf import settings logging.basicConfig(level=logging.INFO, format="%(asctime)s:%(levelname)s:%(message)s") def to_string(value): text = str(value) nmax = settings.LOG_REQUEST_DETAIL_MAX_LENGTH if nmax > 0 and len(text) > nmax: text = text[:nmax] + "......" return text def user_ip_address(request): x_forwarded_for = request.META.get('HTTP_X_FORWARDED_FOR', None) if x_forwarded_for: remote_address = x_forwarded_for.split(',')[0].strip() else: remote_address = request.META.get('REMOTE_ADDR', None) return remote_address class LoggingMiddleware(MiddlewareMixin): """ Log requests and responses Adapted from: https://scripting4ever.wordpress.com/2020/07/27/how-to-log-the-request-and-response-via-django-middleware/ """ def process_request(self, request): if settings.LOG_REQUEST_DETAILS: logging.info("=" * 80) logging.info( "Request Method: " + to_string(request.META.get("REQUEST_METHOD", "???")) ) logging.info("URL requested: " + to_string(request.path)) logging.info("Request Body Contents: " + to_string(request.body)) logging.info("Request Headers: " + to_string(request.headers)) logging.info( "Content Length: " + to_string(request.META.get("CONTENT_LENGTH", "???")) ) logging.info( #"Client IP Address: " + to_string(request.META.get("REMOTE_ADDR", "???")) "Client IP Address: " + to_string(user_ip_address(request)) ) logging.info( "Host Name of Client: " + to_string(request.META.get("REMOTE_HOST", "???")) ) logging.info( "Host Name or Server: " + to_string(request.META.get("SERVER_NAME", "???")) ) logging.info( "Port of the Server: " + to_string(request.META.get("SERVER_PORT", "???")) ) logging.info("-" * 80) return None def process_response(self, request, response): if settings.LOG_REQUEST_DETAILS: logging.info("Response Content: " + to_string(response.content)) logging.info("Response Code: " + to_string(response.status_code)) logging.info("Response Headers: " + to_string(response.headers)) logging.info("=" * 80) return response
then, in settings.py:
MIDDLEWARE = [ ... 'main.middleware.LoggingMiddleware', ] ... LOG_REQUEST_DETAILS = True LOG_REQUEST_DETAIL_MAX_LENGTH = 200
Adapted from:
Using requests:
import requests # https://stackoverflow.com/questions/16694907/download-large-file-in-python-with-requests#16696317 def download_file(url): local_filename = url.split('/')[-1] # NOTE the stream=True parameter below with requests.get(url, stream=True) as r: r.raise_for_status() with open(local_filename, 'wb') as f: for chunk in r.iter_content(chunk_size=8192): # If you have chunk encoded response uncomment if # and set chunk_size parameter to None. #if chunk: f.write(chunk) return local_filename
Using urlib.request:
import urllib.request def download_file2(url): """ Use urlib.request instead of requests to avoid "403 Forbidden" errors when the remote server tries to prevent scraping (for example when is protected behind cloudflare) """ request = urllib.request.Request(url) request.add_header('User-Agent', 'Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:106.0) Gecko/20100101 Firefox/106.0') request.add_header('Accept', 'text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,*/*;q=0.8') request.add_header('Accept-Language', 'en-US,en;q=0.5') response = urllib.request.urlopen(request) local_filename = url.split('/')[-1] chunk_size = 8192 with open(local_filename, 'wb') as f: size = 0 while True: info = response.read(chunk_size) if len(info) < 1: break size = size + len(info) f.write(info) return local_filename
Using requests:
import requests # https://stackoverflow.com/questions/16694907/download-large-file-in-python-with-requests#16696317 def download_file(url): local_filename = url.split('/')[-1] # NOTE the stream=True parameter below with requests.get(url, stream=True) as r: r.raise_for_status() with open(local_filename, 'wb') as f: for chunk in r.iter_content(chunk_size=8192): # If you have chunk encoded response uncomment if # and set chunk_size parameter to None. #if chunk: f.write(chunk) return local_filename
Using urlib.request:
import urllib.request def download_file2(url): """ Use urlib.request instead of requests to avoid "403 Forbidden" errors when the remote server tries to prevent scraping (for example when is protected behind cloudflare) """ request = urllib.request.Request(url) request.add_header('User-Agent', 'Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:106.0) Gecko/20100101 Firefox/106.0') request.add_header('Accept', 'text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,*/*;q=0.8') request.add_header('Accept-Language', 'en-US,en;q=0.5') response = urllib.request.urlopen(request) local_filename = url.split('/')[-1] chunk_size = 8192 with open(local_filename, 'wb') as f: size = 0 while True: info = response.read(chunk_size) if len(info) < 1: break size = size + len(info) f.write(info) return local_filename
My implementation:
import csv from django.db import models from django.db import connection from django.utils import timezone from django.db import connection from django.contrib.humanize.templatetags.humanize import intcomma from ccms_lib.backend.models import CODE_MAX_LENGTH class SqlViewMixin(): @classmethod def create_view(cls, verbose=False): view_name = cls._meta.db_table cls_sql = cls.sql().strip() if cls_sql.endswith(';'): cls_sql = cls_sql[:-1] if cls.materialized: sql = f"CREATE materialized VIEW IF NOT EXISTS {view_name} AS " sql += cls_sql + ';\n' pk_name = cls._meta.pk.name sql += f'CREATE UNIQUE INDEX IF NOT EXISTS idx_{view_name} ON {view_name}({pk_name});' else: sql = f"CREATE VIEW {view_name} AS " sql += cls_sql + ';\n' cls.execute(sql, verbose) @classmethod def drop_view(cls, verbose=False): view_name = cls._meta.db_table sql = "DROP %sVIEW IF EXISTS %s CASCADE;\n" % ( 'materialized ' if cls.materialized else '', view_name, ) pk_name = cls._meta.pk.name sql += f"DROP INDEX IF EXISTS idx_{view_name};" cls.execute(sql, verbose) @classmethod def refresh_view(cls, concurrently=False, verbose=False): if cls.materialized: #sql = "REFRESH MATERIALIZED VIEW CONCURRENTLY {cls._meta.db_table};" sql = "REFRESH MATERIALIZED VIEW %s%s;" % ( "CONCURRENTLY " if concurrently else '', cls._meta.db_table, ) cls.execute(sql, verbose) @classmethod def execute(cls, sql, verbose): with connection.cursor() as cursor: if verbose: print(sql) cursor.execute(sql) @classmethod def export_view_as_csv(cls, verbose, filename=None, delimiter=','): def export_rows(cursor, sql, offset, page_size, writer, verbose): if page_size > 0: sql = sql + " OFFSET %d LIMIT %d" % (offset, page_size) if verbose: print(sql) cursor.execute(sql) if offset <= 0: writer.writerow([f.name for f in cursor.description]) for row in cursor.fetchall(): writer.writerow(row) view_name = cls._meta.db_table if filename is None: filename = timezone.now().strftime('%Y-%m-%d_%H-%M-%S__') + view_name + '.csv' #page_size = 100000 # 0 = no pagination page_size = 1000000 # 0 = no pagination sql = str(cls.objects.all().query) sql += ' ORDER BY "%s"' % cls._meta.pk.name n = 0 step = 0 if verbose: n = cls.objects.count() step = int(n / 100) print('Exporting file "%s"; records: %s' % (filename, intcomma(n))) with open(filename, 'w', newline='') as csvfile: writer = csv.writer(csvfile, dialect='excel', delimiter=delimiter) with connection.cursor() as cursor: if page_size <= 0: # no pagination cursor.execute(sql) writer.writerow([f.name for f in cursor.description]) j = 0 row = cursor.fetchone() while row is not None: j += 1 if verbose and j==1 or ((j/10) % step) == 0: progress = int((j * 100) / n) + 1 print('%d%% (%s/%s)' % (progress, intcomma(j), intcomma(n))) writer.writerow(row) row = cursor.fetchone() else: # paginate num_pages = (n // page_size) + (1 if n % page_size else 0) offset = 0 j = 0 while offset < n: if verbose: progress = int(((j*page_size) * 100) / n) print('page %d/%d (%d%%)' % (j+1, num_pages, progress)) export_rows(cursor, sql, offset, page_size, writer, verbose=False) offset += page_size j += 1 ################################################################################ # Example ... class DwhBase(SqlViewMixin, models.Model): materialized = True id = models.CharField(null=False, max_length=256, primary_key=True) base_code = models.CharField(max_length=CODE_MAX_LENGTH, null=False) base_name = models.CharField(max_length=256, null=False) class Meta: managed = False db_table = "dwhm_base" def __str__(self): return str(self.id) @staticmethod def sql(): return """ SELECT code AS id, code as base_code, description AS base_name FROM backend_base; """
References:
My implementation:
import csv from django.db import models from django.db import connection from django.utils import timezone from django.db import connection from django.contrib.humanize.templatetags.humanize import intcomma from ccms_lib.backend.models import CODE_MAX_LENGTH class SqlViewMixin(): @classmethod def create_view(cls, verbose=False): view_name = cls._meta.db_table cls_sql = cls.sql().strip() if cls_sql.endswith(';'): cls_sql = cls_sql[:-1] if cls.materialized: sql = f"CREATE materialized VIEW IF NOT EXISTS {view_name} AS " sql += cls_sql + ';\n' pk_name = cls._meta.pk.name sql += f'CREATE UNIQUE INDEX IF NOT EXISTS idx_{view_name} ON {view_name}({pk_name});' else: sql = f"CREATE VIEW {view_name} AS " sql += cls_sql + ';\n' cls.execute(sql, verbose) @classmethod def drop_view(cls, verbose=False): view_name = cls._meta.db_table sql = "DROP %sVIEW IF EXISTS %s CASCADE;\n" % ( 'materialized ' if cls.materialized else '', view_name, ) pk_name = cls._meta.pk.name sql += f"DROP INDEX IF EXISTS idx_{view_name};" cls.execute(sql, verbose) @classmethod def refresh_view(cls, concurrently=False, verbose=False): if cls.materialized: #sql = "REFRESH MATERIALIZED VIEW CONCURRENTLY {cls._meta.db_table};" sql = "REFRESH MATERIALIZED VIEW %s%s;" % ( "CONCURRENTLY " if concurrently else '', cls._meta.db_table, ) cls.execute(sql, verbose) @classmethod def execute(cls, sql, verbose): with connection.cursor() as cursor: if verbose: print(sql) cursor.execute(sql) @classmethod def export_view_as_csv(cls, verbose, filename=None, delimiter=','): def export_rows(cursor, sql, offset, page_size, writer, verbose): if page_size > 0: sql = sql + " OFFSET %d LIMIT %d" % (offset, page_size) if verbose: print(sql) cursor.execute(sql) if offset <= 0: writer.writerow([f.name for f in cursor.description]) for row in cursor.fetchall(): writer.writerow(row) view_name = cls._meta.db_table if filename is None: filename = timezone.now().strftime('%Y-%m-%d_%H-%M-%S__') + view_name + '.csv' #page_size = 100000 # 0 = no pagination page_size = 1000000 # 0 = no pagination sql = str(cls.objects.all().query) sql += ' ORDER BY "%s"' % cls._meta.pk.name n = 0 step = 0 if verbose: n = cls.objects.count() step = int(n / 100) print('Exporting file "%s"; records: %s' % (filename, intcomma(n))) with open(filename, 'w', newline='') as csvfile: writer = csv.writer(csvfile, dialect='excel', delimiter=delimiter) with connection.cursor() as cursor: if page_size <= 0: # no pagination cursor.execute(sql) writer.writerow([f.name for f in cursor.description]) j = 0 row = cursor.fetchone() while row is not None: j += 1 if verbose and j==1 or ((j/10) % step) == 0: progress = int((j * 100) / n) + 1 print('%d%% (%s/%s)' % (progress, intcomma(j), intcomma(n))) writer.writerow(row) row = cursor.fetchone() else: # paginate num_pages = (n // page_size) + (1 if n % page_size else 0) offset = 0 j = 0 while offset < n: if verbose: progress = int(((j*page_size) * 100) / n) print('page %d/%d (%d%%)' % (j+1, num_pages, progress)) export_rows(cursor, sql, offset, page_size, writer, verbose=False) offset += page_size j += 1 ################################################################################ # Example ... class DwhBase(SqlViewMixin, models.Model): materialized = True id = models.CharField(null=False, max_length=256, primary_key=True) base_code = models.CharField(max_length=CODE_MAX_LENGTH, null=False) base_name = models.CharField(max_length=256, null=False) class Meta: managed = False db_table = "dwhm_base" def __str__(self): return str(self.id) @staticmethod def sql(): return """ SELECT code AS id, code as base_code, description AS base_name FROM backend_base; """
References:
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