PythonQuickies
Abstract Base Class
from abc import ABC, abstractmethod
from .event import Event
class ThreadEvent(ABC, Event):
"""
A class used to represent a post, comment, or reply in a community.
"""
@abstractmethod
def to_tag(self):
"""
Returns
-------
list
contains one element which is this event's own tag
"""
pass
buffering
Fix CLI buffering in Python with:
$ python -u foo.py | tee mylog.log
"-u" means unbuffered, or something
Caching
Disable __pycache__ Caching
$ python -B foo.py
export PYTHONDONTWRITEBYTECODE=1 python script.py
Datetime and Timestamp
from datetime import datetime, timezone
import pytz
print("When including time, use one of the following:")
ts = 0
good_dt = pytz.utc.localize(datetime.utcfromtimestamp(ts))
print(f'pytz.utc.localize(datetime.utcfromtimestamp(ts)) = {good_dt}')
ts = 0
good_dt = datetime.fromtimestamp(ts, timezone.utc)
print(f'datetime.fromtimestamp(ts, timezone.utc) = {good_dt}')
dt_with_tz = good_dt
good_ts = int(dt_with_tz.timestamp())
print(f'int(dt_with_tz.timestamp()) = {good_ts}')
now_dt = pytz.utc.localize(datetime.utcnow())
now_ts = int(now_dt.timestamp())
renow_dt = datetime.fromtimestamp(now_ts, timezone.utc)
print()
print(f'now_dt = pytz.utc.localize(datetime.utcnow()) = {now_dt}')
print(f'now_ts = int(now_dt.timestamp()) = {now_ts}')
print(f'now_dt = datetime.fromtimestamp(now_ts, timezone.utc) = {renow_dt}')
now_ts = int(pytz.utc.localize(datetime.utcnow()).timestamp())
print(f'now_ts = int(pytz.utc.localize(datetime.utcnow()).timestamp()) = {now_ts}')
import time
print(f'now_ts = int(time.time()) = {int(time.time())}')
Decorators
def my_decorator(func):
def wrapper(*args, **kwargs):
print("Something is happening before the function is called.")
func(*args, **kwargs)
print("Something is happening after the function is called.")
return wrapper
@my_decorator
def say_hello():
print("Hello!")
say_hello()
Delayed Type Definitions
from __future__ import annotations # allows types to be used before definition
class Foo:
def add_child(self, a_foo: Foo)
self.children.append(a_foo)
GUI
- Python GUI
Tkinter
- Tkinter Tutorial: https://www.pythontutorial.net/tkinter/
- Full Screen: root.attributes("-fullscreen", True)
Jupyter
2048 mkdir kiln-jupyter 2049 cd kiln-jupyter/ 2050 python -m venv venv 2051 source venv/bin/activate 2052 pip install jupyter 2053 jupyter-lab 2054 deactivate
MariaDB
pip install mysql-connector-python
import mysql.connector
from mysql.connector import Error
# Establish the connection to the MariaDB database
def create_connection():
try:
connection = mysql.connector.connect(
host="localhost", # or your host
user="your_user",
password="your_password",
database="your_database"
)
if connection.is_connected():
print("Connected to MariaDB")
return connection
except Error as e:
print(f"Error connecting to MariaDB: {e}")
return None
# Function to insert data using a prepared statement
def insert_data(connection, name, age):
try:
cursor = connection.cursor(prepared=True)
sql_insert_query = """INSERT INTO users (name, age) VALUES (%s, %s)"""
data_tuple = (name, age)
cursor.execute(sql_insert_query, data_tuple)
connection.commit()
print("Data inserted successfully")
except Error as e:
print(f"Error: {e}")
finally:
cursor.close()
# Function to fetch data
def fetch_data(connection):
try:
cursor = connection.cursor()
cursor.execute("SELECT id, name, age FROM users")
result = cursor.fetchall()
for row in result:
print(f"ID: {row[0]}, Name: {row[1]}, Age: {row[2]}")
except Error as e:
print(f"Error fetching data: {e}")
finally:
cursor.close()
# Main flow
if __name__ == "__main__":
conn = create_connection()
if conn:
# Insert example data
insert_data(conn, "John Doe", 30)
# Fetch and display data
fetch_data(conn)
# Close the connection
conn.close()
Package Info
Random
base64.b32encode(os.urandom(64)).decode('utf-8')
Sorting
sorted_stories = sorted(stories, key=lambda x: x['job']['ups'], reverse=True)
Subclass
# Parent class
class Vehicle:
def __init__(self, brand, model):
self.brand = brand
self.model = model
def display(self):
print(f"This is a {self.brand} {self.model}.")
# Child class
class Car(Vehicle):
def __init__(self, brand, model, doors):
super().__init__(brand, model) # Call the __init__ of the parent class
self.doors = doors
# Overriding the display method of the parent class
def display(self):
super().display() # Call the display method of the parent class
print(f"It has {self.doors} doors.")
# Testing the classes
vehicle = Vehicle("Toyota", "Camry")
vehicle.display()
car = Car("Honda", "Civic", 4)
car.display()
Type Safety
class Car:
def __init__(self, make: str, year: int) -> None:
self.make = make
self.year = year
def drive(self, speed: float) -> None:
print(f"Driving at {speed} km/h")
def new_model(self, year: int) -> Car:
return Car(self.make, self.year + 1)
# Example usage
car = Car("Toyota", 2022)
car.drive(100.0) # Valid
car.drive("fast") # Invalid, but no runtime error (type checker will warn)
Virtual Environments
# Check Python version
python3 --version
# Check pip version
pip3 --version
# Install virtualenv
pip3 install virtualenv
# Install venv
sudo apt install python3-venv
# Navigate to your project directory
cd ~/my_project/
# Create virtual environment
python3 -m venv myenv
# Activate virtual environment
source myenv/bin/activate
# Now you can install packages
pip install <your-package>
# Deactivate when you're done
deactivate
What Libs Have I?
$ pip freeze --local blinker==1.6.2 click==8.1.7 flask==2.3.3 importlib-metadata==6.8.0 itsdangerous==2.1.2 Jinja2==3.1.2 MarkupSafe==2.1.3 werkzeug==2.3.7 zipp==3.16.2