with sql_context(columns={"x"}):

> Do you support templating a sql tstring into an sql tstring for composition?

Yep

    from sql_tstring import sql
    
    val = 2
    query, values = sql(t"SELECT x FROM y WHERE x = {val}")
    assert query == "SELECT x FROM y WHERE x = ?"
    assert values == [2]
    db.execute(query, values)  # Most DB engines support this

    col = "x"
    sql(t"SELECT {col} FROM y")  # Raises ValueError

    from sql_tstring import sql_context
    
    with sql_context(columns="x"):
        query, values = sql(t"SELECT {col} FROM y")
    assert query == "SELECT x FROM y"
    assert values == []

As t-strings are format strings you can safely format the literals you'd like to pass as variables,

    text = "world"
    query, values = sql(t"SELECT x FROM y WHERE x LIKE '%{text}'")
    assert query == "SELECT x FROM y WHERE x LIKE ?"
    assert values == ["%world"]

SQL-tString is a SQL builder and as such you can use special RewritingValues to alter and build the query you want at runtime. This is best shown by considering a query you sometimes want to search by one column a, sometimes by b, and sometimes both,

    def search(
        *,
        a: str | AbsentType = Absent,
        b: str | AbsentType = Absent
    ) -> tuple[str, list[str]]:
        return sql(t"SELECT x FROM y WHERE a = {a} AND b = {b}")
    
    assert search() == "SELECT x FROM y", []
    assert search(a="hello") == "SELECT x FROM y WHERE a = ?", ["hello"]
    assert search(b="world") == "SELECT x FROM y WHERE b = ?", ["world"]
    assert search(a="hello", b="world") == (
        "SELECT x FROM y WHERE a = ? AND b = ?", ["hello", "world"]
    )

The other rewriting values I've included are handle the frustrating case of comparing to NULL, for example the following is valid but won't work as you'd likely expect,

    optional = None
    sql(t"SELECT x FROM y WHERE x = {optional}")

    from sql_tstring import IsNull

    optional = IsNull
    query, values = sql(t"SELECT x FROM y WHERE x = {optional}")
    assert query == "SELECT x FROM y WHERE x IS NULL"
    assert values == []

The final feature allows for complex query building by nesting a t-string within the existing,

    inner = t"x = 'a'"
    query, _ = sql(t"SELECT x FROM y WHERE {inner}")
    assert query == "SELECT x FROM y WHERE x = 'a'"

Comments URL: https://news.ycombinator.com/item?id=44004827

Points: 85

# Comments: 35

    @tasks.cron("*/5 * * * *")  # every 5 minutes
    async def infrequent_task():
        ...

https://medium.com/smarkets/implementing-gcra-in-python-5df1... https://en.m.wikipedia.org/wiki/Generic_cell_rate_algorithm

This means that you can use the same framework API and understanding to write synchronous code with Flask, and asynchronous code with Quart.

It is important to note that Flask cannot be made asynchronous without breaking extension and backwards compatibility, or without using monkeypatching. Therefore, Quart is best viewed as a namespace for async/await usages.

Questions and comments very welcome. (I'm struggling a little thinking about how best to communicate this)

Comments URL: https://news.ycombinator.com/item?id=37724032

Points: 20

# Comments: 7

I blog mostly about Python web developed, especially Flask, Quart and Hypercorn related aspects.

Comments URL: https://news.ycombinator.com/item?id=34677695

Points: 2

# Comments: 0

1. Quart, https://quart.palletsprojects.com, an ASGI (async/await) re-implementation of the Python web MicroFramework Flask. It is now maintained alongside, by the same people, as Flask.

2. Hypercorn, https://hypercorn.readthedocs.io, an ASGI/WSGI server that supports HTTP/1, HTTP/2, and HTTP/3.

3. My book "A Blueprint for Production-Ready Web Applications", which uses both of the above and shows a beginner how to build a full stack app (React frontend) running on AWS. See https://pgjones.dev/tozo/ for details, code, and link to the example app.

Also see Quart https://github.com/pgjones/quart (which is Flask re-implemented with async-await) and Quart-Schema, https://github.com/pgjones/quart-schema for swagger docs.

Comments URL: https://news.ycombinator.com/item?id=31948086

Points: 4

# Comments: 0