basicco 4.2.2

Collection of lower-level utilities that enhance code compatibility and validation.

Motivation

While developing Python software for Visual Effects pipelines, I found myself having to write the same boiler-plate code over and over again, as well as struggling with compatibility issues and feature gaps between Python 2.7 and Python 3.7+.

So I decided to implement solutions for those issues at the base, and basicco was born.

Overview

Basicco provides a collection of lower-level Utilities that enhance code readability and validation.

Utilities

caller_module

Retrieve the caller’s module name.

>>> from basicco.caller_module import caller_module
>>> def do_something():
...     return "I was called by {}".format(caller_module())
...
>>> do_something()
'I was called by __main__'

context_vars

Rough implementation of ContextVar for Python 2.7 that works with threads.

>>> from basicco.context_vars import ContextVar
>>> my_var = ContextVar("my_var", default="bar")
>>> token = my_var.set("foo")
>>> my_var.get()
'foo'
>>> my_var.reset(token)
>>> my_var.get()
'bar'

custom_repr

Custom representation functions.

>>> from basicco.custom_repr import mapping_repr
>>> dct = {"a": 1, "b": 2}
>>> mapping_repr(dct, prefix="<", suffix=">", template="{key}={value}", sorting=True)
"<'a'=1, 'b'=2>"

>>> from basicco.custom_repr import iterable_repr
>>> tup = ("a", "b", "c", 1, 2, 3)
>>> iterable_repr(tup, prefix="<", suffix=">", value_repr=str)
'<a, b, c, 1, 2, 3>'

explicit_hash

Metaclass that forces __hash__ to be declared when __eq__ is declared.

>>> import six
>>> from basicco.explicit_hash import ExplicitHashMeta
>>> class Asset(six.with_metaclass(ExplicitHashMeta, object)):
...     def __eq__(self, other):
...         pass
...
Traceback (most recent call last):
TypeError: declared '__eq__' in 'Asset' but didn't declare '__hash__'

fabricate_value

Run a value through a callable factory (or None).

>>> from basicco.fabricate_value import fabricate_value
>>> fabricate_value(None, 3)
3
>>> fabricate_value(str, 3)
'3'
>>> fabricate_value("str", 3)  # use an import path
'3'

import_path

Generate importable dot paths and import from them.

>>> import itertools
>>> from basicco.import_path import get_path, import_path
>>> get_path(itertools.chain)
'itertools.chain'
>>> import_path("itertools.chain")
<... 'itertools.chain'>

>>> from basicco.import_path import extract_generic_paths
>>> extract_generic_paths("Tuple[int, str]")
('Tuple', ('int', 'str'))

mangling

Functions to mangle/unmangle/extract private names.

>>> from basicco.mangling import mangle, unmangle, extract
>>> mangle("__member", "Foo")
'_Foo__member'
>>> unmangle("_Foo__member", "Foo")
'__member'
>>> extract("_Foo__member")
('__member', 'Foo')

mapping_proxy

Mapping Proxy type (read-only) for older Python versions.

>>> from basicco.mapping_proxy import MappingProxyType
>>> internal_dict = {"foo": "bar"}
>>> proxy_dict = MappingProxyType(internal_dict)
>>> proxy_dict["foo"]
'bar'

namespace

Wraps a dictionary/mapping and provides attribute-style access to it.

>>> from basicco.namespace import Namespace
>>> ns = Namespace({"bar": "foo"})
>>> ns.bar
'foo'

>>> from basicco.namespace import MutableNamespace
>>> ns = MutableNamespace({"bar": "foo"})
>>> ns.foo = "bar"
>>> ns.foo
'bar'
>>> ns.bar
'foo'

Also provides a NamespacedMeta metaclass for adding a __namespace__ private property that is unique to each class.

>>> from six import with_metaclass
>>> from basicco.namespace import NamespacedMeta
>>> class Asset(with_metaclass(NamespacedMeta, object)):
...     pass
...
>>> Asset.__namespace__.foo = "bar"

qualname

Python 2.7 compatible way of getting the qualified name. Inspired by wbolster/qualname.

recursive_repr

Decorator that prevents infinite recursion for __repr__ methods.

>>> from basicco.recursive_repr import recursive_repr
>>> class MyClass(object):
...
...     @recursive_repr
...     def __repr__(self):
...         return "MyClass<{!r}>".format(self)
...
>>> my_obj = MyClass()
>>> repr(my_obj)
'MyClass<...>'

runtime_final

Runtime-checked version of the typing.final decorator.

Can be used on methods, properties, classmethods, staticmethods, and classes that have FinalizedMeta as a metaclass. It is also recognized by static type checkers and prevents subclassing and/or member overriding during runtime:

>>> import six
>>> from basicco.runtime_final import FinalizedMeta, final
>>> @final
... class Asset(six.with_metaclass(FinalizedMeta, object)):
...     pass
...
>>> class SubAsset(Asset):
...     pass
...
Traceback (most recent call last):
TypeError: can't subclass final class 'Asset'

>>> import six
>>> from basicco.runtime_final import FinalizedMeta, final
>>> class Asset(six.with_metaclass(FinalizedMeta, object)):
...     @final
...     def method(self):
...         pass
...
>>> class SubAsset(Asset):
...     def method(self):
...         pass
Traceback (most recent call last):
TypeError: can't override final member 'method'

>>> import six
>>> from basicco.runtime_final import FinalizedMeta, final
>>> class Asset(six.with_metaclass(FinalizedMeta, object)):
...     @property
...     @final
...     def prop(self):
...         pass
...
>>> class SubAsset(Asset):
...     @property
...     def prop(self):
...         pass
Traceback (most recent call last):
TypeError: can't override final member 'prop'

scrape_class

Scrape a class and get a dictionary with filtered named members. This will respect the MRO (supports multiple inheritance).

>>> from basicco.scrape_class import scrape_class
>>> class Field(object):
...     pass
...
>>> class Asset(object):
...     name = Field()
...     version = Field()
...
>>> class SubAsset(Asset):
...     sub_name = Field()
...
>>> def field_filter(base, member_name, member):
...     return isinstance(member, Field)
>>> sorted(scrape_class(SubAsset, field_filter))
['name', 'sub_name', 'version']

type_checking

Runtime type checking with support for import paths.

>>> from itertools import chain
>>> from basicco.type_checking import is_instance
>>> class SubChain(chain):
...     pass
...
>>> is_instance(3, int)
True
>>> is_instance(3, (chain, int))
True
>>> is_instance(3, ())
False
>>> is_instance(SubChain(), "itertools.chain")
True
>>> is_instance(chain(), "itertools.chain", subtypes=False)
True
>>> is_instance(SubChain(), "itertools.chain", subtypes=False)
False

Asserting an instance’s type:

>>> from itertools import chain
>>> from basicco.type_checking import assert_is_instance
>>> class SubChain(chain):
...     pass
...
>>> assert_is_instance(3, int)
3
>>> assert_is_instance(3, (chain, int))
3
>>> assert_is_instance(3, ())
Traceback (most recent call last):
ValueError: no types were provided to perform assertion
>>> assert_is_instance(3, "itertools.chain")
Traceback (most recent call last):
TypeError: got 'int' object, expected instance of 'chain' or any of its subclasses
>>> assert_is_instance(chain(), "itertools.chain", subtypes=False)
<itertools.chain object at ...>
>>> assert_is_instance(SubChain(), "itertools.chain", subtypes=False)
Traceback (most recent call last):
TypeError: got 'SubChain' object, expected instance of 'chain' (instances of subclasses are not accepted)

unique_iterator

Iterator that yields unique values.

>>> from basicco.unique_iterator import unique_iterator
>>> list(unique_iterator([1, 2, 3, 3, 4, 4, 5]))
[1, 2, 3, 4, 5]