2222</ code > </ pre > </ div > </ td > </ tr > </ table > </ div > < p > Lines 1 to 11 are the imports. The only thing to note here is that we are using the < code > AsyncGenerator</ code > type hint for the < code > get_db</ code > function. This is because we are using the < code > yield</ code > keyword in the function, which makes it a generator. The < code > AsyncGenerator</ code > type hint is a special type hint that is used for asynchronous generators.</ p > < h2 id =database-connection-string > Database Connection String</ h2 > < div class =highlight > < table class =highlighttable > < tr > < td class =linenos > < div class =linenodiv > < pre > < span > </ span > < span class =normal > 13</ span >
2323< span class =normal > 14</ span > </ pre > </ div > </ td > < td class =code > < div > < pre > < span > </ span > < code > < span class =n > DATABASE_URL</ span > < span class =o > =</ span > < span class =s2 > "postgresql+asyncpg://postgres:postgres@localhost/postgres"</ span >
2424< span class =c1 > # DATABASE_URL = "sqlite+aiosqlite:///./test.db"</ span >
25- </ code > </ pre > </ div > </ td > </ tr > </ table > </ div > < p > We set a variable to be used later which contains the database URL. We are using PostgreSQL, but you can use any database that SQLAlchemy supports. The commented out line is for SQLite, which is a good choice for testing. You can comment out the PostgreSQL line (< strong > 13</ strong > )and uncomment the SQLite line (< strong > 14</ strong > )to use SQLite instead.</ p > < p > This is a basic connection string, in reality you would want to use environment variables to store the user/password and database name.</ p > < h2 id =the-base-class > The Base Class</ h2 > < div class =highlight > < table class =highlighttable > < tr > < td class =linenos > < div class =linenodiv > < pre > < span > </ span > < span class =normal > 20</ span >
25+ </ code > </ pre > </ div > </ td > </ tr > </ table > </ div > < p > We set a variable to be used later which contains the database URL. We are using PostgreSQL, but you can use any database that SQLAlchemy supports. The commented out line is for SQLite, which is a good choice for testing. You can comment out the PostgreSQL line (< strong > 13</ strong > ) and uncomment the SQLite line (< strong > 14</ strong > ) to use SQLite instead.</ p > < p > This is a basic connection string, in reality you would want to use environment variables to store the user/password and database name.</ p > < h2 id =the-base-class > The Base Class</ h2 > < div class =highlight > < table class =highlighttable > < tr > < td class =linenos > < div class =linenodiv > < pre > < span > </ span > < span class =normal > 20</ span >
2626< span class =normal > 21</ span >
2727< span class =normal > 22</ span >
2828< span class =normal > 23</ span >
7979< span class =sd > In a real-life example we would use Alembic to manage migrations.</ span >
8080< span class =sd > """</ span >
8181 < span class =k > async</ span > < span class =k > with</ span > < span class =n > async_engine</ span > < span class =o > .</ span > < span class =n > begin</ span > < span class =p > ()</ span > < span class =k > as</ span > < span class =n > conn</ span > < span class =p > :</ span >
82- < span class =c1 > # await conn.run_sync(Base.metadata.drop_all) # noqa: ERA001 </ span >
82+ < span class =c1 > # await conn.run_sync(Base.metadata.drop_all)</ span >
8383 < span class =k > await</ span > < span class =n > conn</ span > < span class =o > .</ span > < span class =n > run_sync</ span > < span class =p > (</ span > < span class =n > Base</ span > < span class =o > .</ span > < span class =n > metadata</ span > < span class =o > .</ span > < span class =n > create_all</ span > < span class =p > )</ span >
84- </ code > </ pre > </ div > </ td > </ tr > </ table > </ div > < p > This function shows how to run a < code > syncronous</ code > function in an < code > async</ code > context using the < code > async_engine</ code > object directly instead of the < code > async_session</ code > object. On line < strong > 57</ strong > we use the < code > run_sync</ code > method to run the < code > create_all</ code > method of the < code > Base.metadata</ code > object (a syncronous function). This will create all of the tables defined in the models.</ p > < p > Next, we will look at the models themselves and the Schemas used to validate them within FastAPI.</ p > </ article > </ div > < script > var target = document . getElementById ( location . hash . slice ( 1 ) ) ; target && target . name && ( target . checked = target . name . startsWith ( "__tabbed_" ) ) </ script > </ div > </ main > < footer class =md-footer > < nav class ="md-footer__inner md-grid " aria-label =Footer > < a href =../intro/ class ="md-footer__link md-footer__link--prev " aria-label ="Previous: Introduction "> < div class ="md-footer__button md-icon "> < svg xmlns =http://www.w3.org/2000/svg viewbox ="0 0 24 24 "> < path d ="M20 11v2H8l5.5 5.5-1.42 1.42L4.16 12l7.92-7.92L13.5 5.5 8 11h12Z "/> </ svg > </ div > < div class =md-footer__title > < span class =md-footer__direction > Previous </ span > < div class =md-ellipsis > Introduction </ div > </ div > </ a > < a href =../models/ class ="md-footer__link md-footer__link--next " aria-label ="Next: Models and Schemas "> < div class =md-footer__title > < span class =md-footer__direction > Next </ span > < div class =md-ellipsis > Models and Schemas </ div > </ div > < div class ="md-footer__button md-icon "> < svg xmlns =http://www.w3.org/2000/svg viewbox ="0 0 24 24 "> < path d ="M4 11v2h12l-5.5 5.5 1.42 1.42L19.84 12l-7.92-7.92L10.5 5.5 16 11H4Z "/> </ svg > </ div > </ a > </ nav > < div class ="md-footer-meta md-typeset "> < div class ="md-footer-meta__inner md-grid "> < div class =md-copyright > < div class =md-copyright__highlight > © 2023-2024 Grant Ramsay (Seapagan) </ div > Made with < a href =https://squidfunk.github.io/mkdocs-material/ target =_blank rel =noopener > Material for MkDocs </ a > </ div > < div class =md-social > < a href =https://www.gnramsay.com target =_blank rel =noopener title =www.gnramsay.com class =md-social__link > < svg xmlns =http://www.w3.org/2000/svg viewbox ="0 0 24 24 "> < path d ="M16.36 14c.08-.66.14-1.32.14-2 0-.68-.06-1.34-.14-2h3.38c.16.64.26 1.31.26 2s-.1 1.36-.26 2m-5.15 5.56c.6-1.11 1.06-2.31 1.38-3.56h2.95a8.03 8.03 0 0 1-4.33 3.56M14.34 14H9.66c-.1-.66-.16-1.32-.16-2 0-.68.06-1.35.16-2h4.68c.09.65.16 1.32.16 2 0 .68-.07 1.34-.16 2M12 19.96c-.83-1.2-1.5-2.53-1.91-3.96h3.82c-.41 1.43-1.08 2.76-1.91 3.96M8 8H5.08A7.923 7.923 0 0 1 9.4 4.44C8.8 5.55 8.35 6.75 8 8m-2.92 8H8c.35 1.25.8 2.45 1.4 3.56A8.008 8.008 0 0 1 5.08 16m-.82-2C4.1 13.36 4 12.69 4 12s.1-1.36.26-2h3.38c-.08.66-.14 1.32-.14 2 0 .68.06 1.34.14 2M12 4.03c.83 1.2 1.5 2.54 1.91 3.97h-3.82c.41-1.43 1.08-2.77 1.91-3.97M18.92 8h-2.95a15.65 15.65 0 0 0-1.38-3.56c1.84.63 3.37 1.9 4.33 3.56M12 2C6.47 2 2 6.5 2 12a10 10 0 0 0 10 10 10 10 0 0 0 10-10A10 10 0 0 0 12 2Z "/> </ svg > </ a > < a href =https://github.com/seapagan target =_blank rel =noopener title =github.com class =md-social__link > < svg xmlns =http://www.w3.org/2000/svg viewbox ="0 0 496 512 "> <!-- Font Awesome Free 6.5.1 by @fontawesome - 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84+ </ code > </ pre > </ div > </ td > </ tr > </ table > </ div > < p > This function shows how to run a < code > syncronous</ code > function in an < code > async</ code > context using the < code > async_engine</ code > object directly instead of the < code > async_session</ code > object. On line < strong > 57</ strong > we use the < code > run_sync</ code > method to run the < code > create_all</ code > method of the < code > Base.metadata</ code > object (a syncronous function). This will create all of the tables defined in the models.</ p > < p > If you want to drop the tables and recreate them every time the server restarts, you can uncomment line < strong > 56</ strong > . This is obviously not much good for production use, but it can be useful for testing.</ p > < p > Next, we will look at the models themselves and the Schemas used to validate them within FastAPI.</ p > </ article > </ div > < script > var target = document . getElementById ( location . hash . slice ( 1 ) ) ; target && target . name && ( target . checked = target . name . startsWith ( "__tabbed_" ) ) </ script > </ div > </ main > < footer class =md-footer > < nav class ="md-footer__inner md-grid " aria-label =Footer > < a href =../intro/ class ="md-footer__link md-footer__link--prev " aria-label ="Previous: Introduction "> < div class ="md-footer__button md-icon "> < svg xmlns =http://www.w3.org/2000/svg viewbox ="0 0 24 24 "> < path d ="M20 11v2H8l5.5 5.5-1.42 1.42L4.16 12l7.92-7.92L13.5 5.5 8 11h12Z "/> </ svg > </ div > < div class =md-footer__title > < span class =md-footer__direction > Previous </ span > < div class =md-ellipsis > Introduction </ div > </ div > </ a > < a href =../models/ class ="md-footer__link md-footer__link--next " aria-label ="Next: Models and Schemas "> < div class =md-footer__title > < span class =md-footer__direction > Next </ span > < div class =md-ellipsis > Models and Schemas </ div > </ div > < div class ="md-footer__button md-icon "> < svg xmlns =http://www.w3.org/2000/svg viewbox ="0 0 24 24 "> < path d ="M4 11v2h12l-5.5 5.5 1.42 1.42L19.84 12l-7.92-7.92L10.5 5.5 16 11H4Z "/> </ svg > </ div > </ a > </ nav > < div class ="md-footer-meta md-typeset "> < div class ="md-footer-meta__inner md-grid "> < div class =md-copyright > < div class =md-copyright__highlight > © 2023-2024 Grant Ramsay (Seapagan) </ div > Made with < a href =https://squidfunk.github.io/mkdocs-material/ target =_blank rel =noopener > Material for MkDocs </ a > </ div > < div class =md-social > < a href =https://www.gnramsay.com target =_blank rel =noopener title =www.gnramsay.com class =md-social__link > < svg xmlns =http://www.w3.org/2000/svg viewbox ="0 0 24 24 "> < path d ="M16.36 14c.08-.66.14-1.32.14-2 0-.68-.06-1.34-.14-2h3.38c.16.64.26 1.31.26 2s-.1 1.36-.26 2m-5.15 5.56c.6-1.11 1.06-2.31 1.38-3.56h2.95a8.03 8.03 0 0 1-4.33 3.56M14.34 14H9.66c-.1-.66-.16-1.32-.16-2 0-.68.06-1.35.16-2h4.68c.09.65.16 1.32.16 2 0 .68-.07 1.34-.16 2M12 19.96c-.83-1.2-1.5-2.53-1.91-3.96h3.82c-.41 1.43-1.08 2.76-1.91 3.96M8 8H5.08A7.923 7.923 0 0 1 9.4 4.44C8.8 5.55 8.35 6.75 8 8m-2.92 8H8c.35 1.25.8 2.45 1.4 3.56A8.008 8.008 0 0 1 5.08 16m-.82-2C4.1 13.36 4 12.69 4 12s.1-1.36.26-2h3.38c-.08.66-.14 1.32-.14 2 0 .68.06 1.34.14 2M12 4.03c.83 1.2 1.5 2.54 1.91 3.97h-3.82c.41-1.43 1.08-2.77 1.91-3.97M18.92 8h-2.95a15.65 15.65 0 0 0-1.38-3.56c1.84.63 3.37 1.9 4.33 3.56M12 2C6.47 2 2 6.5 2 12a10 10 0 0 0 10 10 10 10 0 0 0 10-10A10 10 0 0 0 12 2Z "/> </ svg > </ a > < a href =https://github.com/seapagan target =_blank rel =noopener title =github.com class =md-social__link > < svg xmlns =http://www.w3.org/2000/svg viewbox ="0 0 496 512 "> <!-- Font Awesome Free 6.5.1 by @fontawesome - 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