dagstd 0.1.3

Dagstd

Dagstd is a Python package containing a set of helper modules for use with the Dagster data orchestration tool.

Dagster is a great tool, but there are occasions where you just need to pass in a simple integer or string as input to a Dagster op, but in Dagster, inputs to ops can only be outputs of other ops. This results in a lot of boilerplate functions being written that just return a formatted string or even just an integer. This is why Dagstd was created.

Features

• Simple ops for common numbers

• Constant value ops

• Helper ops for mathematical and string operations

• Ops for retrieving environment variables

• Sphinx autodoc support for Dagster ops

Usage

Here’s an example of a pure-Dagster graph that downloads a daily zip file and extracts a known file name. Note: the download_large_file op has been omitted for brevity.

import zipfile

from datetime import datetime

from dagster import op, job


@op
def get_todays_date() -> str:
    return datetime.today().strftime()


@op
def five() -> int:
    return 5


@op
def get_download_file_url(date: str) -> str:
    return f'https://example.com/{date}.csv'


@op
def get_nth_file_name(n: int) -> str:
    return f'file_{n:02}.txt'


@op
def extract_file_from_zip(context, zip_path: str, file_name: str) -> str:
    with zipfile.ZipFile(zip_path) as zip_file:
        with(f'/tmp/{file_name}', 'wb') as f:
            f.write(zip_file.read(file_name))
        context.log.info(f'Extracted {file_name} from {zip_path}')
        return f'/tmp/{file_name}'


@job
def process_data():
    date = get_todays_date()
    url = get_download_file_url(date)
    zip_path = download_large_file(url)

    file_name = get_nth_file_name(five())
    file_path = extract_file_from_zip(zip_path, file_name)

And here’s the same graph, but with Dagstd ops.

import zipfile

from datetime import datetime

from dagster import op, job
from dagstd.constants import Constant, Five
from dagstd.operations import fmt


@op
def get_todays_date_string() -> str:
    return datetime.today().strftime("%Y-%m-%d")


@op
def extract_file_from_zip(context, zip_path: str, file_name: str) -> str:
    with zipfile.ZipFile(zip_path) as zip_file:
        with(f'/tmp/{file_name}', 'wb') as f:
            f.write(zip_file.read(file_name))
        context.log.info(f'Extracted {file_name} from {zip_path}')
        return f'/tmp/{file_name}'


@job
def process_data():
    date = get_todays_date_string()
    url = fmt(Constant('https://example.com/{}.csv'), [date])
    zip_path = download_large_file(url)

    file_name = fmt(Constant('file_{}.txt'), [Five()])
    file_path = extract_file_from_zip(zip_path, file_name)

This was just a small example, but it serves to show how much boilerplate can be avoided when using Dagstd.

Sphinx Autodoc Plugin

Dagstd includes a Sphinx autodoc plugin that can be used to generate documentation for Dagster ops. To use the autodoc plugin, add the following to your conf.py file:

extensions = [
    ...
    'dagstd.sphinx.parser',
]

By default, this will prefix all op documentation with (op). To change this, add the following to your conf.py file:

dagstd_op_prefix = 'My Op'

Documentation

Documentation can be found at https://dagstd.readthedocs.io/en/latest/readme.html.

Installation

Install Dagstd with pip:

pip install dagstd

Dependencies

• dagster >= 0.14.17

Contribute

I’m always looking for more ideas to add to Dagstd. If you have an idea, please open an issue or pull request, or message me on GitHub.

• Issue Tracker: https://github.com/isaacharrisholt/dagstd/issues

• Source Code: https://github.com/isaacharrisholt/dagstd

Support

If you are having issues, please let me know.

License

The project is licensed under the GNU GPLv3 license.