Miscellaneous Python Notes

Python HTTP Server

To spin up an http server, you can use python3 -m http.server to serve a directory over HTTP (port 80). To specify a different port, you can use python3 -m http.server 8080 to serve on port 8080.

Containerizing an Application

To safely share with others, you can containerize an application. Use podman or docker to build the image:

# Use the Python version you need
#FROM python:3.9-slim 
FROM python:3.11

# Set the working directory inside the container
WORKDIR /usr/src/app

# Copy the current directory into the container at the WORKDIR
COPY . .

# Install dependencies (expects a requirements.txt file in the current directory)
RUN pip install --no-cache-dir -r requirements.txt

# Make port 80 available to the world (for web apps)
EXPOSE 80

# Set environment variables
ENV NAME World
ENV PATH /usr/src/app

# Run the app when the container launches
RUN ["python3", "./app.py"]

Then build the image

podman build -t python-app .

and run it

podman run -p 8080:80 python-app

Expanding Iterables for Function Arguments

The * operator can be used to expand iterables into function arguments or to unpack elements from lists, tuples, or other iterable objects.

With dictionaries, the ** operator can be used to unpack key-value pairs into function arguments.

Some examples:

# Expanding a list into function arguments
numbers = [1, 2, 3]
def add(a, b, c):
    print(a + b + c)

add(*numbers) # Expands into `add(1, 2, 3)`

# Expanding a tuple into function arguments
coordinates = (4, 5)
def print_coordinates(x, y):
    print(f"Coordinates: ({x}, {y})")
print_coordinates(*coordinates) # Expands into `print_coordinates(4, 5)`

# Expanding a dictionary into function arguments
person = {'name': 'Alice', 'age': 30}
def greet(name, age):
    print(f"Hello, {name}! You are {age} years old.")

greet(**person) # Expands into `greet(name='Alice', age=30)`

When using a function that accepts variable-length arguments, you can use *args and **kwargs to handle additional positional and keyword arguments, respectively.

positional_args = (1, 2, 3)
keyword_args = {'name': 'Alice', 'age': 30}
def example_function(*args, **kwargs):
    print("Positional arguments:", args)
    print("Keyword arguments:", kwargs)

example_function(*positional_args, **keyword_args)