Posts tagged: python

exclude=True and repr=False is a good pydantic combination for secret attributes such as user passwords, or hashed passwords. exclude keeps it out of model_dumps, and repr keeps it out of the logs.

Hatch be flyin.

This new release of hatch includes support for the new package installer uv which is just mind blowing fast compared to anything else we have in python right now.

[tool.hatch.envs.default] installer = "uv"

The other features are cool too, check them out. I’ll probably be using the test runner, but I’ve been waiting for the uv support since uv launched.

This is my go to rich response container for clis written in python. It creates a nice box around the content on the screen and provides some nice separation in the output. It can be overdone, but comes in clutch when looking for that print statement in a long output.

This page shows how to customize your fastapi errors. I found this very useful to setup common templates so that I can return the same 404’s both programatically and by default, so it all looks the same to the end user.

from fastapi import FastAPI, Request from fastapi.responses import JSONResponse class UnicornException(Exception): def __init__(self, name: str): self.name = name app = FastAPI() @app.exception_handler(UnicornException) async def unicorn_exception_handler(request: Request, exc: UnicornException): return JSONResponse( status_code=418, content={"message": f"Oops! {exc.name} did something. There goes a rainbow..."}, ) @app.get("/unicorns/{name}") async def read_unicorn(name: str): if name == "yolo": raise UnicornException(name=name) return {"unicorn_name": name}

This post sat in draft for months. I stumbled upon it again and found great success returning good error messages based on user...

To allow access only to the , you can pass add the Resource field to the User Policy when you create a new token.

You can inspect sqlite tables with the sqlite shell.

note that you get into the shell with sqlite3 database.db

.tables

I also learned that .tables, .index and .schema are helper functions that query the sqlite_master table on the main database.

Here is an output from my redka database. The sqlite_master table contains all the sqlite objects type, name, tbl_name, rootpage, and sql to create them.

I recently had to update my copier-gallery command to trust my own templates because some of them have shell scripts that run afterwards. Be warned that this could be a dangerous feature to run on random templates you get off the internet, but these are all mine, so if I wreck it its my own fault.

copier copy --trust <template> <destination>

All the the copier copy api can be found with help.

Today I accidentally ran f2 in ipython to discover that it opens your $EDITOR! I use this feature quite often in zsh, it is bound to <c-e> for me, and since I have my environment variable EDITOR set to nvim it opens nvim when I hit <c-e>. Today I discovered that Ipython has this bound to F2. If you know how to set it to <c-e> let me know I’ve tried, a lot.

export EDITOR=nvim ipython <F2>

better yet add export EDITOR=nvim to your .zshrc

I’ve really been enjoying using sqlmodel for my projects that need a database. One thing that I definitely lacked on for too long was indexing my database. I hit a point with one database where it was taking 7s for pretty simple paginated queries to return 10 records.

For every field that you will be querying on, you can create an index, by setting it equal to Field(index=True)

class Hero(SQLModel, table=True): id: int | None = Field(default=None, primary_key=True) name: str = Field(index=True) secret_name: str age: int | None = Field(default=None, index=True)

example courtesy of the docs

The docs cover this pretty well, and in quite depth - Optimizing Queries

This is a cool snapshot testing tool that automatically creates, and updates test values for you.

Starting with some test code.

from inline_snapshot import snapshot def something(): return 1548 * 18489 def test_something(): assert something() == snapshot()

now if I run pytest my tests will fail because my assert will fail, but if I run pytest --inline-snapshot=create it will fill out my snapshot values and the file will then look like this.

inline-snapshot is a new tool that I am trying out for python testing. It takes snapshots of your outputs and places them inline with the test.

Here is the most basic starter.

import inline_snapshot def test_one(): assert 1 == snapshot()

Now when I run pytest my tests will fail because my assert has no value, but if I run pytest --inline-snapshot=create it will fill out my snapshot values and the file will then look like this.

import inline_snapshot def test_one(): assert 1 == snapshot(1)

It also works with pydantic models.

Today I learned how to VACUUM a sqlite database and cut its size in about half. It’s a database that I have had running for quite awhile and has some decent traffic on it.

Why is it important to do a VACUUM? In short its becuase the file system gets fragmented with as data is updated. On delete the files are removed from the database and marked as available for reuse in the filesystem, but the space is not reclaimed.

To VACUUM a database, run the following sql command. You can do it right form the sqlite shell by running sqlite3.

You will need about double the current size of the database as free space to do the VACUUM, you need space for a full copy, journaling or write ahead logs, and the existing database.

...

Typer makes it easy to compose your cli applications, like you might with a web router if you are more familiar with that. This allows you to build smaller applications that compose into a larger application.

You will see similar patterns in the wild, namely the aws cli which always has the aws <command> <subcommand> pattern.

Lets setup the cli app itself first. You can put it in project/cli/cli.py.

import typer from project.cli.api import api_app from project.cli.config import config_app from project.cli.user import user_app from project.cli.run import run_app app = typer.Typer() app.add_typer(api_app, name="api") app.add_typer(config_app, name="config") app.add_typer(user_app, name="user") app.add_typer(run_app, name="run")

Creating an app that will become a command is the same as creating a regular app in Typer. We need to create a callback that will become our command, and a command that will become our subcommand in the parent app.

...

I am working on a page for htmx-patterns and I ran into a situation with lots of duplication. Especially when i am using tailwind I run into situations where the duplication can get tedious to maintiain. The solution I found is macros.

Now I can use the same code for all of my links, and call the macro to use it.

jinja has a loop variable that is very handy to use with htmx. Whether you want to implement a click to load more or an infinite scroll this loop variable is very handy.

{% for person in persons %} <li {% if loop.last %} hx-get="{{ url_for('infinite', page=next_page) }}" hx-trigger="intersect once" hx-target="#persons" hx-swap='beforeend' hx-indicator="#persons-loading" {% endif %} {{ person.name.upper() }} - {{ person.phone_number }} </li> {% endfor %}

Now for every chunk of contacts that we load we will trigger the infinite scroll by loading more once the last one has intersected the screen.

Out of the box FastAPI.">Starlette does not support url_for with query params. When trying to use url_for with query params it throws the following error.

starlette.routing.NoMatchFound: No route exists for name "infinite" and params "page"

In my searching for this I found starlette issue #560 quite helpful, but not complete, as it did not work for me.

import jinja2 if hasattr(jinja2, "pass_context"): pass_context = jinja2.pass_context else: pass_context = jinja2.contextfunction @pass_context def url_for_query(context: dict,...