Common Utilities

utils.md

About

Common Utility functions

Table of Contents

• utils_argparse.py
• utils_config.py
  • read_config
• utils_datetime.py
  • get_month_start_date_from_date
• utils_networking.py
  • download_url_to_file_with_progress_bar
• utils_jinja2.md
  • basic jinja2 templating
• External Resources:
  • Creating database sessions using SQLAlchemy and Flask-SQLAlchemy simultaneously: Link

utils_argparse.py

import argparse

if __name__ == "__main__":
    parser = argparse.ArgumentParser()
    parser.add_argument('--filename', action='store', dest='filename',
                        required=True, help='Some filename.')
    parser.add_argument('--use_cpu', action='store_true', dest='use_cpu',
                        required=False, default=False, help='Use CPU instead GPU.')
    command_args = parser.parse_args()

utils_config.py

"""Config related utilities.

################################################################################
DEPENDENCIES
File: dev_environment.yml
Create Environment: conda env create --force -f dev_environment.yml
################################################################################
name: utils-config
channels:
  - defaults
dependencies:
- python=3.6
- pip:
  - future
  - pyyaml
"""
import yaml


def read_config(config_filename):
    """Read and return config from filename.

    Args:
        config_filename (str): Path to config file

    Returns:
        dict: Config file as a dictionary.
    """
    with open(config_filename, 'r') as f:
        config = yaml.load(f)
    return config

utils_datetime.py

import datetime

def get_month_start_date_from_date(any_date):
    """Return the start date of the month of any date of datetime.

    Args:
        any_date (datetime.datetime or datetime.date): Any date or datetime.

    Returns:
        datetime.date: The start date of the month.
    """
    if isinstance(any_date, datetime.datetime):
        any_date = datetime.date
    elif isinstance(any_date, datetime.date):
        pass
    else:
        raise ValueError("`any_date` must be either datetime.datetime or datetime.date instead it is of type {}."
                         .format(type(any_date)))

    month_start_date = any_date.replace(day=1)
    return month_start_date

utils_flask.md

About

Flask snippets

Snippets

Shared Database Session

db_session.py.

"""Shared database session instantiation.

SOURCE: http://flask.pocoo.org/snippets/22/
"""
from sqlalchemy import create_engine
from sqlalchemy.orm import sessionmaker as SessionMaker
from sqlalchemy.orm import scoped_session

engine = None
sessionmaker = SessionMaker()
db_session = scoped_session(sessionmaker)


def init_engine(uri, **kwargs):
    """."""
    global engine, sessionmaker
    engine = create_engine(uri, **kwargs)
    db_session.remove()
    sessionmaker.configure(bind=engine)
    return engine

server.py

from db_models import db  # module where Tables are declared
from db_session import db_session, init_session

# ...
# Initialize app with database and other wiring
# ...

def register_database(app):
  """Register the app with the database."""
  db.init_app(app)
  with app.app_context():
      # Extensions like Flask-SQLAlchemy now know what the "current" app
      # is while within this block. Thereforse, you can now run........
      db.create_all()
      init_session(db)

utils_jinja2.md

Install Jinja2

pip install Jinja2

Basic Jinja2 Templating

"""Basic Jinja2 Templating."""
from jinja2 import Template

template = Template('Hello {{ name }}!')
template.render(name='John Doe')

utils_networking.py

import requests
from tqdm import tqdm


def download_url_to_file_with_progress_bar(url, filename):
    # Streaming, so we can iterate over the response.
    r = requests.get(url, stream=True)

    # Total size in bytes.
    total_size = int(r.headers.get('content-length', 0))  # Bytes
    write_size = 1000 * 1000  # Bytes, 1MB
    total_iters = (total_size // write_size) + 1

    with open(filename, 'wb') as f:
        for data in tqdm(r.iter_content(write_size), total=total_iters, unit='MB', unit_scale=True):
            f.write(data)