Table of Contents
Snippets
Naming conventions
Specified in PEP-0008:
- Class names are
CamelCase. - Functions are
lower_with_underscores. - Variables are
lower_with_underscores. - Constants are
BLOCK_CAPS.
Typing
You can use the typing module to provide type hints. This is more for documentation since there’s no checking.
from typing import Dict, List, Tuple
Vector = List[float]
def my_func(vec: Vector, thing: MyClass) -> None:
pass
Dataclasses
Using the dataclasses module:
from dataclasses import dataclass
@dataclass
class InventoryItem:
'''Class for keeping track of an item in inventory.'''
name: str
unit_price: float
quantity_on_hand: int = 0
def total_cost(self) -> float:
return self.unit_price * self.quantity_on_hand
item = InventoryItem("Toy", 25.0, 3)
Interfaces
You can use the abc module.
from abc import ABC, abstractmethod
from logic.model import Recipe
class Store(ABC):
@abstractmethod
def add_recipe(self, recipe: Recipe) -> None:
pass
@abstractmethod
def get_recipes(self) -> Recipe:
pass
class InMemoryStore(Store):
# ...
Testing
Use pytest. Install and run with (ensure you’re doing the dependency management bit below):
pip install -U pytest
pytest
Tests are methods that begin with test_ and you use the standard language assert.
Pytest will recursively look for any files named test_*.py or *_test.py (more here).
Web Server
Bottle is a decent web server to use.
from bottle import Bottle, request, route, run
app = Bottle()
@app.route('/')
def hello():
# Query parameters like http://localhost:8080?name=John
name = request.query.name or "Peter"
return "Hello " + name
app.run(host='localhost', port=8080, debug=True)
Dependency Management
To keep your Python environments nice and clean, use VirtualEnv.
TODO: Update this to use venv instead of virtualenv.
Install
pip install --user virtualenv
Project Setup
In the project directory:
virtualenv ENV
This will create an ENV directory.
Usage
Whenever you want to do anything in your project, run:
source ENV/bin/activate
Now you can install things normally with pip, eg:
pip3 install torch torchvision
Once you’re done, run deactivate.
Distributing
To save the state of your environment, run:
pip freeze > requirements.txt
And then somebody else can run:
pip install -r requirements.txt
Python Tools
To start a local HTTP server:
python -m SimpleHTTPServer 8080 # Python 2
python -m http.server 8080 # Python 3