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Erlang-like atoms in Python 3

Project description

Atum is a tiny Python library that you can use to emulate the basic functionality of Erlang’s atom in your Python scripts.

Status: Beta; this is an experiment.

Erlang documentation:

3.3 Atom

An atom is a literal, a constant with name. An atom is to be enclosed in single quotes (’) if it does not begin with a lower-case letter or if it contains other characters than alphanumeric characters, underscore (_), or @. Examples:

hello
phone_number
'Monday'
'phone number'

http://erlang.org/doc/reference_manual/data_types.html

Unlike Erlang’s atom, atum does not impose the same limitations. You may import any valid Python name from atum - even all uppercase.

Install

$ pip install atum

Examples

Instead of writing:

@app.route('/register', methods=['GET', 'POST'])
def register():
    pass

You could write:

from atum import GET, POST

@app.route('/register', methods=[GET, POST])
def register():
    pass

This might be useful if you use autocompletion. Another benefit is exceptions occur sooner in case of typos, since the interpreter itself validates the imported names. Pay attention when importing, simply tab-to-complete later.

You can compare an atum with another atum or a string.

from atum import machine, human

assert human == human
assert machine == machine
assert machine == 'machine'
assert human != machine
assert human is human
assert machine is machine

Atums also make for readable sentinel values or event-names.

from atum import user_is_awake
from queue import Queue

q = Queue()

q.put(user_is_awake)

assert q.get() == user_is_awake

Technical Details

Atum simply imports Python strings with the same content as their name.

Here is the content of atum.py in its entirety:

import sys as _sys

# intern() is a builtin in Python 2.
if _sys.version_info > (3, 0):
    intern = _sys.intern


class Atum(object):
    def __getattr__(self, item):
        if item.startswith('__'):
            return self.__getattribute__(item)
        return intern(item)

    def __getitem__(self, item):
        return item


_sys.modules[__name__] = Atum()

Known Issues

  • Atum does not support using @ in imported names as Python’s syntax does not allow it.

Project details


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