Fast Flask Dev For Big Codebases

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Fast Flask dev for Big Codebases

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Python Mauritius UserGroup (pymug) More info: mscc.mu/python-mauritius-usergroup-pymug/ Why Where codes github.com/pymug share events twitter.com/pymugdotcom ping professionals linkedin.com/company/pymug all info pymug.com tell friends by like facebook.com/pymug 5

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Abdur-Rahmaan Janhangeer Help people get into OpenSource People hire me to work on Python projects www.compileralchemy.com 6

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Fav foreign (https://metabob.com) World's most advanced code analysis tool? Fav local (https://oceandba.com) 7

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Fast Flask dev for Big Codebases 8

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The Flask Story 9

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Begin new project 10

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Code features 11

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Deploy 12

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Refine Deploy 13

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TEST AND PROD ENV DIFFERENT 14

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USE CONFIGURATION PROFILES 15

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ADD APP FACTORY 16

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APP BREAKING 17

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WRITE TESTS 18

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CODE DISORGANISED 19

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ORGANISE CODEBASE 20

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TESTS ARE BORING 21

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WRITE FIXTURES, WRITE SCHEMAS 22

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I HAVE TO START A NEW PROJECT 23

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HAVE A TEMPLATE 24

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NOW I HAVE TO USE APIS 25

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INTEGRATE API-FRAMEWORK 26

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pulls some more hair 27

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I WANT TO INTEGRATE CELERY 28

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INTEGRATE CELERY 29

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dev left ... 30

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THE NEW INTERN DOES NOT UNDERSTAND ANYTHING 31

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WRITE DOCS!!! 32

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You need something that flies in all weather 33

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The Application Factory 34

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def create_app(app_name): app = Flask(app_name) return app 35

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Configuration Profiles 36

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class Config: TESTING = False class ProductionConfig(Config): FAV_FLOWER = 'rose' class DevelopmentConfig(Config): FAV_FLOWER = 'sunflower' class TestingConfig(Config): FAV_FLOWER = 'moonlight petal' TESTING = True 37

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from config import ProductionConfig from config import DevelopmentConfig from config import TestingConfig profiles = { 'development': DevelopmentConfig(), 'production': ProductionConfig(), 'testing': TestingConfig() } def create_app(profile): app = Flask(__name__) app.config.from_object(profiles[profile]) return app 38

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Tests 39

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Use Pytest Use class-based testing Define fixtures for common actions e.g. logout/login 40

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Docs 41

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Use Sphinx from the start 42

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Separate Initialisations From The Factory 43

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Use a file for initialisations Reduces import errors to a max 44

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app.py init.py 45

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init.py db = SQLAlchemy() ma = Marshmallow() login_manager = LoginManager() migrate = Migrate() mail = Mail() 46

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from init import mail def create_app(...): app = ... mail.init_app(app) in other files: from init import db 47

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Use modules for everything!!! 48

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app.py module1/ module2/ module3/ 49

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app.py modules/ module1/ module2/ 50

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module1/ templates/ static/ test/ models.py forms.py view.py etc etc 51

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Use flask to simplify your life 52

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@app.cli.command("jump", short_help="skip something") def jump(): # do something return 0 # cli flask jump 53

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Automate blueprint registration 54

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1. name each blueprint: foldername_blueprint 2. In app.py # pseudocode for folder in modules: blueprint = import(f'modules.{folder}.view.{folder}_blueprint') app.register(blueprint) 55

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Automate module creation 56

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# pseudocode def createmodule(name): mkdir(folder) touch(folder/models.py) touch(folder/) ... # cli flask createmodule apple 57

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Form help yourself 58

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Use flask-wtf Use wtforms-alchemy class ConfForm(ModelForm): class Meta: model = Conf 59

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Contain static in module, implement collecstatic 60

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app.py static/ # served from here in production modules/ m1/ static/ file.png m2/ static/ file.png collectstatic just collects all assets in all modules and add it under app.py static/ modules/ m1/ file.png m2/ file.png 61

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define function serve_asset(module, resource_path) e.g. serve_asset('m1', 'file.png') if mode is dev serve from /modules/m1/static/file.png i.e /modules/module_name/m1/static/path/to/file.png if mode is prod serve from /static/modules/m1/file.png (assumes collecstatic run before) i.e /static/modules/module_name/path/to/file.png 62

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What for celery? 63

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app.py init.py celery_app.py modules/ m1/ task.py 64

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init.py celery = Celery( __name__, broker=BaseConfig.CELERY_BROKER_URL, backend=BaseConfig.CELERY_RESULT_BACKEND, ) 65

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app.py from init import celery def init_celery(app=None): app = create_app(os.getenv("FLASK_ENV", "")) app = app or create_app() celery.conf.update(app.config) class ContextTask(celery.Task): """Make celery tasks work with Flask app context""" def __call__(self, *args, **kwargs): with app.app_context(): return self.run(*args, **kwargs) celery.Task = ContextTask return celery 66

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celery_app.py from app import init_celery celery = init_celery() 67

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modules/m1/task.py from init import celery @celery.task(name="do something", bind=True) def task_do_something(self): 68

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What for flask-restx? 69

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modules/ app.py init.py api_util.py 70

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init.py api = Api( version="1.0", title="MVP Data", description="Backend Part", authorizations=authorizations, ) 71

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api_util.py # from modules.some.api import some_ns from modules.some2.api import some2_ns # ns: namespace from init import api_v1 api_v = api_v1 # /api/v1 def add_api(api): api.add_namespace(some_ns, path=api_v + "/someapi") api.add_namespace(some2_ns, path=api_v + "/someapi2") 72

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app.py from init import api from api_util import add_api def create_app(...): app = ... api.init_app(app) add_api(api) 73

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Migrations to the next level 74

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# make flask-migrate auto detect models for folder in modules: import(f'modules.{folder}.models.py') 75

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Modular migration ideas: make flask_migrate or alembic load only specific classes 76