Skip to content

python_modules_cheat_sheet.md

Latest commit

 

History

History
executable file
·
310 lines (230 loc) · 9.35 KB

python_modules_cheat_sheet.md

File metadata and controls

executable file
·
310 lines (230 loc) · 9.35 KB

Python Modules Cheat Sheet

Quick reference for third-party Python modules used in projects. For full project walk-throughs, including connecting things to your Raspberry Pi, visit https://stem.tiu11.org.

Contents

Need to Install First

Since these Python modules aren't part of the Python Standard Library, they have to be installed. The linked docs will have instructions for Raspberry Pi OS. Look for sudo apt-get update and sudo apt-get install or sometimes sudo pip3 install.

Raspberry Pi GPIO Pins

A simple interface to GPIO devices with Raspberry Pi.

https://gpiozero.readthedocs.io

(gpiozero is installed by default)

The recipes are a great place to start: LED, Button, Reaction Game, Motion sensor, Motors, etc. The pin numbering diagram is helpful if you don't have one in your kit.

from gpiozero import Button, LED, OutputDevice
from time import sleep

# LED
led = LED(17)

led.on()
sleep(1)
led.off()
sleep(1)

# Button

button = Button(3)

print('Press the button!')
button.wait_for_press()
print('Button was pressed!')

# Relay

relay = OutputDevice(24)

relay.on()
sleep(1)
relay.off()

guizero

guizero is a Python 3 library for creating simple GUIs.

It is designed to allow new learners to quickly and easily create GUIs for their programs.

https://lawsie.github.io/guizero/

After installing, check out their Recipes for examples to try out. Try this example to make a PushButton run commands that turn an LED on and off.

from guizero import App, Text, PushButton
from gpiozero import LED

red = LED(12)
app = App(title="GUI with LED Controls")

label = Text(app, text="Red")
on_button = PushButton(app, command=red.on, text="on")
off_button = PushButton(app, command=red.off, text="off")

app.display()

Get fancy with sizes, colors and images.

As your GUI grows, it might get cluttered. Look into Layouts for ways to organize things, like a grid and (Boxes)[https://lawsie.github.io/guizero/layout/#boxes].

Automation HAT

https://github.com/pimoroni/automation-hat

Getting Started Guide | GPIO Pinout guide | Function Reference

import automationhat

value1 = automationhat.analog.one.read()
value2 = automationhat.analog.two.read()

# Check if an input/output/relay is on
if automationhat.input.one.is_on():
  print('One is on')

# Turn an output on or off
automationhat.output.one.on()  # Turn output 1 on
automationhat.output.one.off() # ...and off

Temperature Probe

Get the temperature from a w1 therm compatible sensor.

https://github.com/timofurrer/w1thermsensor

Setup

  • sudo pip3 install w1thermsensor (see installation)
  • Go to Raspberry Pi menu > Preferences > Raspberry Pi Configuration > Interface.
    • Enable 1-wire
    • Reboot
from w1thermsensor import W1ThermSensor
from time import sleep

sensor = W1ThermSensor()
temperature_in_celsius = sensor.get_temperature()

Sense HAT

https://pythonhosted.org/sense-hat/

from sense_hat import SenseHat
from time import sleep

sense = SenseHat()
red = (255, 0, 0)           # RGB levels are 0 to 255

sense.clear(red)            # Fill whole screen red
sleep(1)
sense.clear()               # Fill whole screen blank
sleep(1)
sense.set_pixel(4, 5, red) # Set specific pixel red
sleep(1)
sense.show_message("Pi Yum!!")

r = red             # Red
w = (255, 255, 255) # White
question_mark = [
  w, w, w, r, r, w, w, w,
  w, w, r, w, w, r, w, w,
  w, w, w, w, w, r, w, w,
  w, w, w, w, r, w, w, w,
  w, w, w, r, w, w, w, w,
  w, w, w, r, w, w, w, w,
  w, w, w, w, w, w, w, w,
  w, w, w, r, w, w, w, w
]

sense.set_pixels(question_mark)

Pi Camera

The picamera package for the Raspberry Pi camera module

https://picamera.readthedocs.io/

Test in the Console.

# Show a preview. Press <Ctrl+C> to close the preview.
pi@raspberrypi:~ $ raspistill -k

# Take a picture and save it to a file.
pi@raspberrypi:~ $ raspistill -o image.jpg

Photo

from picamera import PiCamera
from gpiozero import Button
from time import sleep

camera = PiCamera()
button = Button(17)

while True:
  camera.start_preview(alpha=192)
  button.wait_for_press()
  sleep(3)
  camera.capture("/home/pi/button.jpg")
  camera.stop_preview()

Video

from picamera import PiCamera

camera = PiCamera()

camera.start_preview(alpha=192)
camera.framerate = 24
camera.start_recording('/home/pi/myvideo.h264')
camera.wait_recording(5)


camera.stop_recording()
camera.stop_preview()

Minecraft Pi

The mcpi module allows you to communicate with Minecraft: Pi edition.

Install with sudo pip3 install mcpi

from mcpi import minecraft

mc = minecraft.Minecraft.create()

mc.postToChat("Hello world")

Internet Requests

Make HTTP requests on the internet.

https://docs.python-requests.org/en/master/user/quickstart/

HTTP messages are how web browsers communicate on the internet. You make a request to a server (or a computer) and it sends a response back.

  • The main parts of a request are:
    • url - the address a request will go to.
    • method - the "verb" or type of request. We'll cover GET and POST requests.
    • body - (optional) data like a form or a file
    • headers - (optional) like settings. Most of the time, we're happy with the defaults, so just be aware of them.
  • The main parts of a response:
    • actually, it looks a lot like a request, so...all those parts 😄
    • status - a code in the response to your request to let you know if it was successfully completed.
      • 200 OK - the request succeeded
      • 404 Not Found - the server can't find that. Do you have a typo in the url?

POST

An HTTP POST request asks a server to accept data you are sending it. A web browser uses POST when you submit an online form.

import requests

event     = "your IFTTT event name"
api_key   = "your-ifttt-key-here"
ifttt_url = "https://maker.ifttt.com/trigger/%s/with/key/%s" % (event, api_key)
payload   = { "value1" : value1, "value2" : value2, "value3" : value3 }
response  = requests.post(ifttt_url, data=payload)

GET

An HTTP GET request asks a server to send it something. It is used to retrieve data.

Get a Joke

import requests

# Get a joke in JSON format.
response = requests.get('https://official-joke-api.appspot.com/random_joke')
if response.ok:
  joke_data = response.json()
else:
  print("Oops! The joke is on me!")

# Tell the joke
print(joke_data['setup'])
sleep(1) # wait for it!
print(joke_data['punchline'])

Advanced GET Example: Download an image and save it to a file. Uses the MIME type from the response headers, telling us the type of content in the response, to add the right extension to the filename.

import requests
import mimetypes

# Get the location of a random cat picture. Hopefully this is safe.
response = requests.get('https://aws.random.cat/meow')
data = response.json()
file_url = data['file']

# Get the picture.
response = requests.get(file_url)
if response.ok:
  # Name the file so the extension matches the type of image.
  content_type = response.headers['Content-Type']
  extension = mimetypes.guess_extension(content_type) # .png, .gif, ...
  filename = 'random_cat' + extension

  # Save the file, overwriting any existing file with the same name.
  with open(filename, 'wb') as f:
    f.write(response.content)
else:
  print('error when getting ' + file_url)