My Python Cheat Sheet

Note: These examples use Python 3.x, not Python 2.x. Unless you're stuck with some legacy system, you shouldn't use 2.x.

Setting up ConfigParser

First, create a configuration.txt file. (and always make sure to either globally add this to your .gitignore file or do it in the current project!)

[example]
API_KEY=foo

Now you can use it in your programs:

import configparser

config = configparser.ConfigParser()
config.read('configuration.txt')
api_key = config['example'].get('API_KEY')

Slugify a String

Use the python-slugify package:

$ pip install python-slugify

Now you can use it:

>>> import slugify
>>> slugify.slugify("Thé h@ppy dog went ~ and came back!")
the-h-ppy-dog-went-and-came-back

Set up Jinja2 Template Rendering

A number of configuration options need to be set and I have to look them up all the time.

import arrow
import jinja2

# Set up the template engine
template_loader = jinja2.FileSystemLoader('./templates')
template_env = jinja2.Environment(loader=template_loader)
template_env.filters['fmt_date'] = lambda v: arrow.get(v, fmt).format(fmt)

# Write the file
template = template_env.get_template('template.html')
html = template.render(data={})
pathlib.Path('index.html').write_text(html)

Combine Two Equal-Sized Lists into a Dictionary

I use this all the time when working with CSV files.

>>> list1 = ["Column A", "Column B", "Column C"]
>>> list2 = ["Value 1", "Value 2", "Value 3"]
>>> dict(zip(list1, list2))
{'Column B': 'Value 2', 'Column C': 'Value 3', 'Column A': 'Value 1'}

Configuring Argparse

import argparse
import arrow
import pathlib

def valid_date_arg(value):
    """ Used by argparser to validate date arguments """
    try:
        return arrow.get(value, 'YYYY-MM-DD')
    except arrow.parser.ParserError:
        msg = f'Not a valid date in YYYY-MM-DD format: "{value}"'
        raise argparse.ArgumentTypeError(msg)


def valid_filepath_arg(value):
    """ Used by argparse to see if a file exists """
    filepath = pathlib.Path(value)

    if not filepath.exists():
        msg = f'File "{arg}" does not exist'
        raise argparse.ArgumentTypeError(msg)
    else:
        return filepath


def valid_dir_arg(value):
    """ Used by argparse to see if a directory exists """
    filepath = pathlib.Path(value)

    if not filepath.exists() or not filepath.is_dir():
        msg = f'Directory "{arg}" does not exist'
        raise argparse.ArgumentTypeError(msg)
    else:
        return filepath


# Read command-line arguments
argparser = argparse.ArgumentParser()
argparser.add_argument('date', type=valid_date_arg)
argparser.add_argument('directory', type=valid_dir_arg)
args = argparser.parse_args()

Arrow Time Formatting

Here are all the formats you use when formatting an Arrow object:

>>> import arrow
>>> arrow.now().format('YYYY-MM-DD')

Simple Logging

I wrote a simple logging wrapper to simplify setting up logging in a project: https://github.com/greencoder/ezlogs

$ pip install ezlogs

Example usage:

import ezlogs

logger = ezlogs.Logger(file_name='log.txt', console_level='debug', file_level='info')

logger.info('This is an informational message')
logger.debug('This is a debugging message')