fidzu : Python

Locust is a Python library that makes it relatively straightforward to write Python tests. This heavily commented code example explains each section of code. To use locust:

1. Install locust: pip install locust
2. Copy the file below into the directory where you want to run locust
3. In that directory, at the command-line, type: locust
4. Open http://localhost:8089/

# locustfile.py
# For more options read the following
#   - https://docs.locust.io/en/stable/writing-a-locustfile.html
#   - https://docs.locust.io/en/stable/tasksets.html

# Import Locust basics
from locust import HttpUser, SequentialTaskSet, task, between

# Imports for generating content
from string import ascii_letters
from random import randint, shuffle

def namer():
    "Create a random string of letters under 10 characters long"
    ascii_list = list(ascii_letters)
    shuffle(ascii_list)
    return ''.join(ascii_list[:10])

class TaskSet(SequentialTaskSet):
    """
    A class for organizing tasks, inheriting from
    SequentialTaskSet means the tasks happen in order.
    """

    def on_start(self):
        # Methods with the on_start name will be called for each
        # simulated user when they start. Useful for logins and
        # other 'do before doing all other things'.
        pass

    def on_stop(self):
        # Methods with the on_stop name will be called for each
        # simulated user when they stop. Useful for logouts and
        # possibly data cleanup.
        pass    

    # TASKS!
    # Methods marked with the `@task` decorator is an action
    # taken by a user This example focuses on changes to a 
    # database, but provides a foundation for creating tests on
    # a more read-focused site

    @task
    def index(self):
        # User goes to the root of the project
        self.client.get('/')

    @task
    def create(self):
        # User posts a create form with the fields 'name'
        # and 'age'
        with self.client.post('/create', dict(name=namer(), age=randint(1,35))) as resp:
            self.pk =  resp.text

    @task
    def update(self):
        # User posts an update form with the fields 'name'
        # and 'age'"
        form_data = dict(id=self.pk, name=namer(), age=randint(1,35))
        self.client.post(f'/{self.pk}/update', form_data)

    @task
    def delete(self):
        # Represents the user getting a random ID and then
        # going to the delete page for it.
        self.client.get(f'/{self.pk}/delete')

class CatsiteUser(HttpUser):
    """
    This class represents simulated users interacting with
    a website.
    """
    # What tasks should be done    
    tasks = [TaskSet]
    # how long between clicks a user should take
    wait_time = between(2, 5)
    # The default host of the target client. This can be changed
    # at any time
    host = 'http://localhost:5001/'    

Sample test site

For reference, this is the test site used to create the above locustfile. I'll admit that the above test is incomplete, a lot more tasks could be added to hit web routes. To use it:

1. Install FastHTML: pip install python-fasthtml
2. Copy the file into the directory you want to run it
3. In that directory, at the command-line, type: python cats.py
4. Open http://localhost:5001/

# cats.py
from fasthtml.common import *

# Set up the database and table
db = database('cats.db')
class Cat: name:str; age:int; id:int
cats = db.create(Cat, pk='id', transform=True)

# Instantiate FastHTML app and route handler
app, rt = fast_app()

def mk_form(target: str):
    return Form(
            P(A('Home', href=index)),
            Fieldset(
                Input(name='name'),
                Input(name='age', type='number'),

            ),
            Input(type='submit', value='submit'),
            method='post'
        )

def cat_count():
    query = """select count(id) from cat;"""
    result = db.execute(query)
    return result.fetchone()[0]

@rt
def index():
    return Titled('Cats',
        P(A('Create cat', href='/create'), NotStr(' '), A('Random ID', href=random)),
        P(f'Number of cats: {cat_count()}'),        
        Ol(
            *[Li(A(f'{d.name}:{d.age}', href=f'/{d.id}')) for d in cats()]
        )
    )

@rt
def random():
    # Small datasets so we can get away with using the RANDOM() function here
    query = """SELECT id FROM cat ORDER BY RANDOM() LIMIT 1;"""
    result = db.execute(query)
    return result.fetchone()[0]

@rt('/create')
def get():
    return Titled('Create Cat', 
        mk_form('/create')
    )

@rt('/create')
def post(cat: Cat):
    while True:
        try:
            cat = cats.insert(Cat(name=cat.name, age=cat.age))
            break
        except Exception as e:
            print(e)
            raise
    return cat.id

@rt('/{id}')
def cat(id: int):
    cat = cats[id]
    return Titled(cat.name, 
        P(cat.age),
        P(A('update', href=f'/{id}/update')),
        P(A('delete', href=f'/{id}/delete')),
    )


@rt('/{id}/update')
def get(id: int):
    cat = cats[id]
    return Titled('Edit Cat',
        fill_form(mk_form(f'/{cat.id}/update'), cat)
    )

@rt('/{id}/update')
def post(cat: Cat, id: int):
    if id not in cats:
        return RedirectResponse(url=index)
    cat.id = id
    db.begin()
    try:
        cats.update(cat)
        db.commit()        
    except:
        db.rollback()
    return RedirectResponse(url=f'/{cat.id}')

@rt('/{id}/delete')
def cat(id: int):
    if id not in cats:
        RedirectResponse(url=index)
    # db.begin()
    cats.delete(id)
    # db.commit()
    return RedirectResponse(url=index)

serve()

Updates

• 2024-11-08 Use SequentialTaskSet as recommended by Audrey Roy Greenfeld
• 2024-11-08 Fixed a few bugs in cats.py

25 Dec 2024 3:14am GMT

Did you know that Python's types library has a bunch class implementation? How did I not see this before?!

25 Dec 2024 3:14am GMT

Run

A run launches a child process in a new bash within bash, so variables last only the lifetime of the command. This is why launching Python environments doesn't use run.

./list-things.sh

Source

A source is the current bash, so variables last beyond the running of a script. This is why launching Python environments use source.

source ~/.venv/bin/activate

25 Dec 2024 3:14am GMT

Until now I didn't use this HTMX technique, but today Audrey Roy Greenfeld and I dove in together to figure it out. Note that we use language that may not match HTMX's description, sometimes it's better to put things into our own words so we understand it better.

from fasthtml.common import *

app,rt = fast_app()

def mk_row(name, email):
    return Tbody(
        # Only the Tr element and its children is being
        # injected, the Tbody isn't being injected
        Tr(Td(name), Td(email)),
        # This tells HTMX to inject this row at the end of
        # the #contacts-tbody DOM element
        hx_swap_oob="beforeend:#contacts-tbody",
    ),

@rt
def index():
    return Div(
            H2("Contacts"),
            Table(
                Thead(Tr(Th("Name"), Th("Email"))),
                Tbody(
                    Tr(Td("Audrey"), Td("mommy@example.com")),
                    Tr(Td("Uma"), Td("kid@example.com")),
                    Tr(Td("Daniel"), Td("daddy@example.com")),
                    # Identifies the contacts-tbody DOM element
                    id="contacts-tbody",
                ), 
            ),
            H2("Add a Contact"),
            Form(
                Label("Name", Input(name="name", type="text")),
                Label("Email", Input(name="email", type="email")),
                Button("Save"),
                hx_post="/contacts",
                # Don't swap out the contact form
                hx_swap='none',
                # Reset the form and put focus onto the name field
                hx_on__after_request="this.reset();this.name.focus();"
            )
        )

@rt
def contacts(name:str,email:str):
    print(f"Adding {name} and {email} to table")
    return mk_row(name,email)

serve()

To verify the behavior, view the rendered elements in your browser of choice before, after, and during submitting the form.

25 Dec 2024 3:14am GMT

SequentialTaskSet makes it so Locust tasks happen in a particular order, which ensures your simulated users are clicking around in a more human manner at a more human pace. Attribution goes to Audrey Roy Greenfeld.

You can see it in action in the now updated previous entry on the topic of Locust for load testing.

25 Dec 2024 3:14am GMT

I've never really paid attention to this object but maybe I should have. It takes a single argument of a callable function. If you put in Python types it sets the default value to those types. For example, if I use an int at the instantiating argument then it gives us a zero.

>>> from collections import defaultdict
>>>
>>> mydict = defaultdict(int)
>>> print(mydict['anykey'])
0

Note that defaultdict also act like regular dictionaries, in that you can set keys. So mydict['me'] = 'danny' will work as you expect it to with a standard dictionary.

It gets more interesting if we pass in a more dynamic function. In the exmaple below we use random.randint and a lambda to make the default value be a random number between 1 and 100.

>>> from random import randint
>>>
>>> random_values = defaultdict(lambda: randint(1,100))

Let's try it out!

>>> for i in range(5):
>>>     print(random_values[i])
>>> print(random_values)
29
90
56
42
70
defaultdict(<function <lambda> at 0x72d292bb6de0>, {0: 29, 1: 90, 2: 56, 3: 42, 4: 70})

Attribution goes to Laksman Prasad, who pointing this out and encouraging me to closer look at defaultdict.

25 Dec 2024 3:14am GMT

The function way

Until today I did this:

# Make first dict
num_map = {
    'one': '1', 'two': '2', 'three': '3', 'four': '4',
    'five': '5', 'six': '6', 'seven': '7', 'eight': '8',
    'nine': '9'
}
# Add second dict
num_map.update({str(x):str(x) for x in range(1,10)})
print(num_map)

The operator way

Now thanks to Audrey Roy Greenfeld now I know I can do this:

# Make first dict while adding second dict
num_map = {
    'one': '1', 'two': '2', 'three': '3', 'four': '4',
    'five': '5', 'six': '6', 'seven': '7', 'eight': '8',
    'nine': '9'
} | {str(x):str(x) for x in range(1,10)}
print(num_map)

25 Dec 2024 3:14am GMT

alias pdb='pytest --pdb --pdbcls=IPython.terminal.debugger:TerminalPdb'

Usage:

pdb tests/test_things::test_broken_thing

25 Dec 2024 3:14am GMT

jupyter notebook password

Attribution for this goes to Johno Whitaker.

25 Dec 2024 3:14am GMT

In the past when I've done this for web pages and various other interfaces it has been a mess. I've built ungainly sort order in numeric or alphanumeric batches. Inevitably there is a conflict, often sooner rather than later. So sorting a list of things often means updating all the elements to preserve the order in the datastore. I've learned to mark each element with a big value, but it's ugly and ungainly

Fortunately for me, going forward, I now know about Fractional Indexing.

References:

• https://www.figma.com/blog/realtime-editing-of-ordered-sequences/
• https://observablehq.com/@dgreensp/implementing-fractional-indexing
• https://github.com/httpie/fractional-indexing-python

25 Dec 2024 3:14am GMT

Add these commands to the top of a notebook within a Python cell. Thanks to Jeremy Howard for the tip.

%load_ext autoreload
%autoreload 2

25 Dec 2024 3:14am GMT

I'm excited to have learned there's a word for the count of arguments to a function/method/class: arity. Throughout my career I would have called this any of the following:

• number_of_args
• param_count
• numargs
• intArgumentCount

Thanks to Simon Willison for using it in a library or two and making me look up the word.

25 Dec 2024 3:14am GMT

#661 - DECEMBER 24, 2024
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Articles & Tutorials

Projects & Code

Events

Happy Pythoning!
This was PyCoder's Weekly Issue #661.
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24 Dec 2024 7:30pm GMT

Sarah Abderemane, Thibaud Colas and Tom Carrick are pleased to introduce four new members in the Django Accessibility team ❤️.

Marijke Luttekes

Eliana Rosselli

Tushar Gupta

Saptak Sengupta

Marijke (pronounced Mah-Rye-Kuh) is a freelance web developer who creates human-friendly applications. She is based in Groningen, The Netherlands, specializing in Django, Python, HTML, SCSS, and vanilla JavaScript. She helps companies expand their existing projects, think about new features, train new developers, and improve developer team workflows. She is aDdjango contributor from the first session of Djangonaut Space program and she loves tea. You can learn more about Marijke on her website.

Eli is a full-stack developer from Uruguay who loves using Django and React. She is a Django contributor from the first session of the Djangonaut Space program

. She is passionate about good quality code, unit testing, and web accessibility. She enjoys drinking Maté (and talking about it!) and watching her football team play.

Tushar is a software engineer at Canonical, based in India. He got involved on open source during his studies loving the the supportive community. Through fellowships like Major League Hacking, Tushar dove into Django and took part in Djangonaut Space. Learn more about Tushar on his personal website.

Saptak is a self-proclaimed Human Rights Centered Developer Web. He focuses on security, privacy, accessibility, localization, and other human rights associated with websites that makes websites more inclusive and usable by everyone. Learn more about Saptak on his personal website.

Listen to them talking about their work¶

Here are recent talks or podcasts from our new team members if you want to get to know them better.

Marijke Luttekes - My path to becoming a Django contributor | pyGrunn 2024 Eli Rosselli - My step-by-step guide to becoming a Django core contributor | DjangoCon Europe 2024 Tushar Gupta - Djangonauts, Ready for Blast-Off | Talk Python to Me Ep.451 Saptak S - Accessibility for the Django Community | DjangoCon Europe 2024

What's next¶

In truth, our four new accessibility team members joined the team months ago - shortly after we published our 2023 accessibility team report. Up next, a lot of the team will be present at FOSDEM 2025, organizing, volunteering, or speaking at the Inclusive Web Devroom.

24 Dec 2024 2:00pm GMT

If you're a Django developer, I'm sure you've heard so many people raving about FastAPI and Pydantic. But you really love Django and don't want to switch. Then you might want to give Django Ninja a serious look. Django Ninja is highly inspired by FastAPI, but is also deeply integrated into Django itself. We have Vitaliy Kucheryaviy the creator of Django Ninja on this show to tell us all about it.<br/> <br/> <strong>Episode sponsors</strong><br/> <br/> <a href='https://talkpython.fm/sentry'>Sentry Error Monitoring, Code TALKPYTHON</a><br> <a href='https://talkpython.fm/bluehost'>Bluehost</a><br> <a href='https://talkpython.fm/training'>Talk Python Courses</a><br/> <br/> <h2>Links from the show</h2> <div><strong>Vitaly</strong>: <a href="https://github.com/vitalik?featured_on=talkpython" target="_blank" >github.com/vitalik</a><br/> <strong>Vitaly on X</strong>: <a href="https://x.com/vital1k?featured_on=talkpython" target="_blank" >@vital1k</a><br/> <br/> <strong>Top 5 Episodes of 2024</strong>: <a href="https://talkpython.fm/blog/posts/top-talk-python-podcast-episodes-of-2024/" target="_blank" >talkpython.fm/blog/posts/top-talk-python-podcast-episodes-of-2024</a><br/> <br/> <strong>Django Ninja</strong>: <a href="https://django-ninja.dev/?featured_on=talkpython" target="_blank" >django-ninja.dev</a><br/> <strong>Motivation section we talked through</strong>: <a href="https://django-ninja.dev/motivation/?featured_on=talkpython" target="_blank" >django-ninja.dev/motivation</a><br/> <strong>LLM for Django Ninja</strong>: <a href="https://llm.django-ninja.dev/?featured_on=talkpython" target="_blank" >llm.django-ninja.dev</a><br/> <strong>Nano Django</strong>: <a href="https://github.com/vitalik/nano-django?featured_on=talkpython" target="_blank" >github.com/vitalik/nano-django</a><br/> <strong>Episode transcripts</strong>: <a href="https://talkpython.fm/episodes/transcript/490/django-ninja" target="_blank" >talkpython.fm</a><br/> <br/> <strong>--- Stay in touch with us ---</strong><br/> <strong>Subscribe to Talk Python on YouTube</strong>: <a href="https://talkpython.fm/youtube" target="_blank" >youtube.com</a><br/> <strong>Talk Python on Bluesky</strong>: <a href="https://bsky.app/profile/talkpython.fm" target="_blank" >@talkpython.fm at bsky.app</a><br/> <strong>Talk Python on Mastodon</strong>: <a href="https://fosstodon.org/web/@talkpython" target="_blank" ><i class="fa-brands fa-mastodon"></i>talkpython</a><br/> <strong>Michael on Bluesky</strong>: <a href="https://bsky.app/profile/mkennedy.codes?featured_on=talkpython" target="_blank" >@mkennedy.codes at bsky.app</a><br/> <strong>Michael on Mastodon</strong>: <a href="https://fosstodon.org/web/@mkennedy" target="_blank" ><i class="fa-brands fa-mastodon"></i>mkennedy</a><br/></div>

24 Dec 2024 8:00am GMT

Starting in Python 3.9, s.removeprefix() and s.removesuffix() were added as str built-ins. Which easily covers all the versions of Python I currently support.

Usage for removeprefix():

>>> 'Spam, Spam'.removeprefix('Spam')
', Spam'
>>> 'Spam, Spam'.removeprefix('This is not in the prefix')
'Spam, Spam'

Usage for removesuffix():

>>> 'Spam, Spam'.removesuffix('Spam')
'Spam, '
>>> 'Spam, Spam'.removesuffix('This is not in the suffix')
'Spam, Spam'

23 Dec 2024 7:03pm GMT