Source code for presets

#!/usr/bin/env python
# -*- encoding: utf-8 -*-
"""Presets provides an object interface to a module which can override \
the default parameter values.

This is primarily useful for packages which contain many functions with
overlapping parameter sets.  Presets can be used to consistently override
all defaults at once, while maintaining the same externally-facing API.

Example
-------
This example shows how to override common default parameters in the
librosa package.

>>> import librosa as _librosa
>>> from presets import Preset
>>> librosa = Preset(_librosa)
>>> librosa['sr'] = 44100
>>> librosa['n_fft'] = 4096
>>> librosa['hop_length'] = 1024
>>> y, sr = librosa.load(librosa.util.example_audio_file())
>>> stft = librosa.stft(y)
>>> tempo, beats = librosa.beat.beat_track(y)
"""

import inspect
import os
import types

import functools


short_version = '1.0'
version = '1.0.0'
__version__ = version


[docs] class Preset(object): """The Preset class overrides the default parameters of functions \ within a module. If the given module contains submodules, these are also encapsulated by Preset objects that share the same default parameter dictionary. Submodules are detected by examining common prefixes of the module source paths. Attributes ---------- module : Python module The module to encapsulate dispatch : None or dictionary A dictionary mapping modules to existing Preset objects. This should be left as `None` for most situations. defaults : None or dictionary An existing dictionary object used to collect default parameters. Note: this will be passed by reference. """ def __wrap(self, func): """Override the default arguments of a function. For each keyword argument in the function, the decorator first checks if the argument has been overridden by the caller, and uses that value instead if so. If not, the decorator consults the Preset object for an override value. If both of the above cases fail, the decorator reverts to the function's native default parameter value. """ def deffunc(*args, **kwargs): """Decorate the given function.""" # Get the list of function arguments function_args = inspect.signature(func).parameters # Construct a dict of those kwargs which appear in the function filtered_kwargs = kwargs.copy() # look at all relevant keyword arguments for this function for param in function_args: if param in kwargs: # Did the user override the default? filtered_kwargs[param] = kwargs[param] elif param in self._defaults: # Do we have a clobbering value in the default dict? filtered_kwargs[param] = self._defaults[param] # Call with the supplied args and the filtered kwarg dict return func(*args, **filtered_kwargs) # pylint: disable=W0142 wrapped = functools.update_wrapper(deffunc, func) # force-mangle the docstring here wrapped.__doc__ = ( 'WARNING: this function has been modified by the Presets ' 'package.\nDefault parameter values described in the ' f'documentation below may be inaccurate.\n\n{wrapped.__doc__}') return wrapped def __init__(self, module, dispatch=None, defaults=None): """Initialize Preset object around a given module.""" # This defaults directory will get passed around by reference if defaults is None: defaults = dict() self._defaults = defaults self._module = module if dispatch is None: dispatch = dict() dispatch[module] = self self._dispatch = dispatch modpath = os.path.dirname(inspect.getfile(module)) # inspect the target module for attr, value in inspect.getmembers(module): # If it's a function, wrap it if callable(value): # Wrap the function in a decorator wrapped = self.__wrap(value) setattr(self, attr, wrapped) # If it's a module, construct a parameterizer to wrap it elif (isinstance(value, types.ModuleType) and hasattr(value, '__file__')): # test if this is a submodule of the current module submodpath = inspect.getfile(value) if os.path.commonprefix([modpath, submodpath]) == modpath: if value not in self._dispatch: # We need to pre-seed the dispatch entry to avoid # cyclic references self._dispatch[value] = None self._dispatch[value] = Preset(value, dispatch=self._dispatch, defaults=self._defaults) setattr(self, attr, self._dispatch[value]) else: setattr(self, attr, value) def __getitem__(self, param): """Implement dictionary interface (get) to presets object.""" return self._defaults[param] def __delitem__(self, param): """Implement dictionary interface (del) to presets object.""" del self._defaults[param] def __contains__(self, param): """Implement dictionary interface (in) to presets object.""" return param in self._defaults def __setitem__(self, param, value): """Implement dictionary interface (set) to presets object.""" self._defaults[param] = value
[docs] def keys(self): """Return a list of currently set parameter defaults.""" return self._defaults.keys()
[docs] def update(self, D): """Update the default parameter set with the provided dictionary D.""" self._defaults.update(D)