Created
April 29, 2016 15:05
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Metaclass idea for file patterns
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from functools import wraps | |
from inspect import Parameter, Signature | |
# ---------------------------------------------------------- | |
# Helper Regular Expression str builders | |
# ---------------------------------------------------------- | |
def add_regex_start_end(pattern_function): | |
"""Decorator for adding regex pattern start and end characters.""" | |
@wraps(pattern_function) | |
def func_wrapper(*args, **kwargs): | |
return r'^{}$'.format(pattern_function(*args, **kwargs)) | |
return func_wrapper | |
PACKAGE_RE = r'[a-z][a-z_]*[a-z]' | |
VERSION_RE = r'[0-9]{1,3}' | |
PACKAGE_FMT = r'(?P<package>{package})?_?' | |
VERSION_FMT = r'v(?P<version>{version!s})' | |
_package_template = PACKAGE_FMT + '_' + VERSION_FMT + '_schema' | |
_KEYWORD_MAP = {'package': PACKAGE_RE, 'version': VERSION_RE} | |
def make_sig(*names): | |
parameters = [Parameter(name, Parameter.POSITIONAL_OR_KEYWORD, default=_KEYWORD_MAP[name]) | |
for name in names] | |
return Signature(parameters) | |
class TemplateMeta(type): | |
def __new__(cls, clsname, bases, clsdict): | |
fields = clsdict.get('_fields', []) | |
clsdict['__signature__'] = make_sig(*fields) | |
return super().__new__(cls, clsname, bases, clsdict) | |
class PackagePattern(metaclass=TemplateMeta): | |
template = _package_template | |
_fields = ['package', 'version'] | |
_kw_map = _KEYWORD_MAP | |
def __init__(self, *args, **kwargs): | |
print(self.__signature__) | |
bound_values = self.__signature__.bind(*args, **kwargs) | |
bound_values.apply_defaults() | |
print(bound_values) | |
arguments = bound_values.arguments | |
for name, parameter in self.__signature__.parameters.items(): | |
setattr(self, name, arguments.get(name, parameter.default)) | |
@add_regex_start_end | |
def __call__(self, **kwargs) -> str: | |
params = {**self.__dict__, **kwargs} | |
return self.template.format_map(params) |
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