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Diffstat (limited to 'hypervideo_dl/utils/traversal.py')
| -rw-r--r-- | hypervideo_dl/utils/traversal.py | 254 |
1 files changed, 254 insertions, 0 deletions
diff --git a/hypervideo_dl/utils/traversal.py b/hypervideo_dl/utils/traversal.py new file mode 100644 index 0000000..462c3ba --- /dev/null +++ b/hypervideo_dl/utils/traversal.py @@ -0,0 +1,254 @@ +import collections.abc +import contextlib +import inspect +import itertools +import re + +from ._utils import ( + IDENTITY, + NO_DEFAULT, + LazyList, + int_or_none, + is_iterable_like, + try_call, + variadic, +) + + +def traverse_obj( + obj, *paths, default=NO_DEFAULT, expected_type=None, get_all=True, + casesense=True, is_user_input=False, traverse_string=False): + """ + Safely traverse nested `dict`s and `Iterable`s + + >>> obj = [{}, {"key": "value"}] + >>> traverse_obj(obj, (1, "key")) + "value" + + Each of the provided `paths` is tested and the first producing a valid result will be returned. + The next path will also be tested if the path branched but no results could be found. + Supported values for traversal are `Mapping`, `Iterable` and `re.Match`. + Unhelpful values (`{}`, `None`) are treated as the absence of a value and discarded. + + The paths will be wrapped in `variadic`, so that `'key'` is conveniently the same as `('key', )`. + + The keys in the path can be one of: + - `None`: Return the current object. + - `set`: Requires the only item in the set to be a type or function, + like `{type}`/`{func}`. If a `type`, returns only values + of this type. If a function, returns `func(obj)`. + - `str`/`int`: Return `obj[key]`. For `re.Match`, return `obj.group(key)`. + - `slice`: Branch out and return all values in `obj[key]`. + - `Ellipsis`: Branch out and return a list of all values. + - `tuple`/`list`: Branch out and return a list of all matching values. + Read as: `[traverse_obj(obj, branch) for branch in branches]`. + - `function`: Branch out and return values filtered by the function. + Read as: `[value for key, value in obj if function(key, value)]`. + For `Iterable`s, `key` is the index of the value. + For `re.Match`es, `key` is the group number (0 = full match) + as well as additionally any group names, if given. + - `dict` Transform the current object and return a matching dict. + Read as: `{key: traverse_obj(obj, path) for key, path in dct.items()}`. + + `tuple`, `list`, and `dict` all support nested paths and branches. + + @params paths Paths which to traverse by. + @param default Value to return if the paths do not match. + If the last key in the path is a `dict`, it will apply to each value inside + the dict instead, depth first. Try to avoid if using nested `dict` keys. + @param expected_type If a `type`, only accept final values of this type. + If any other callable, try to call the function on each result. + If the last key in the path is a `dict`, it will apply to each value inside + the dict instead, recursively. This does respect branching paths. + @param get_all If `False`, return the first matching result, otherwise all matching ones. + @param casesense If `False`, consider string dictionary keys as case insensitive. + + The following are only meant to be used by YoutubeDL.prepare_outtmpl and are not part of the API + + @param is_user_input Whether the keys are generated from user input. + If `True` strings get converted to `int`/`slice` if needed. + @param traverse_string Whether to traverse into objects as strings. + If `True`, any non-compatible object will first be + converted into a string and then traversed into. + The return value of that path will be a string instead, + not respecting any further branching. + + + @returns The result of the object traversal. + If successful, `get_all=True`, and the path branches at least once, + then a list of results is returned instead. + If no `default` is given and the last path branches, a `list` of results + is always returned. If a path ends on a `dict` that result will always be a `dict`. + """ + casefold = lambda k: k.casefold() if isinstance(k, str) else k + + if isinstance(expected_type, type): + type_test = lambda val: val if isinstance(val, expected_type) else None + else: + type_test = lambda val: try_call(expected_type or IDENTITY, args=(val,)) + + def apply_key(key, obj, is_last): + branching = False + result = None + + if obj is None and traverse_string: + if key is ... or callable(key) or isinstance(key, slice): + branching = True + result = () + + elif key is None: + result = obj + + elif isinstance(key, set): + assert len(key) == 1, 'Set should only be used to wrap a single item' + item = next(iter(key)) + if isinstance(item, type): + if isinstance(obj, item): + result = obj + else: + result = try_call(item, args=(obj,)) + + elif isinstance(key, (list, tuple)): + branching = True + result = itertools.chain.from_iterable( + apply_path(obj, branch, is_last)[0] for branch in key) + + elif key is ...: + branching = True + if isinstance(obj, collections.abc.Mapping): + result = obj.values() + elif is_iterable_like(obj): + result = obj + elif isinstance(obj, re.Match): + result = obj.groups() + elif traverse_string: + branching = False + result = str(obj) + else: + result = () + + elif callable(key): + branching = True + if isinstance(obj, collections.abc.Mapping): + iter_obj = obj.items() + elif is_iterable_like(obj): + iter_obj = enumerate(obj) + elif isinstance(obj, re.Match): + iter_obj = itertools.chain( + enumerate((obj.group(), *obj.groups())), + obj.groupdict().items()) + elif traverse_string: + branching = False + iter_obj = enumerate(str(obj)) + else: + iter_obj = () + + result = (v for k, v in iter_obj if try_call(key, args=(k, v))) + if not branching: # string traversal + result = ''.join(result) + + elif isinstance(key, dict): + iter_obj = ((k, _traverse_obj(obj, v, False, is_last)) for k, v in key.items()) + result = { + k: v if v is not None else default for k, v in iter_obj + if v is not None or default is not NO_DEFAULT + } or None + + elif isinstance(obj, collections.abc.Mapping): + result = (try_call(obj.get, args=(key,)) if casesense or try_call(obj.__contains__, args=(key,)) else + next((v for k, v in obj.items() if casefold(k) == key), None)) + + elif isinstance(obj, re.Match): + if isinstance(key, int) or casesense: + with contextlib.suppress(IndexError): + result = obj.group(key) + + elif isinstance(key, str): + result = next((v for k, v in obj.groupdict().items() if casefold(k) == key), None) + + elif isinstance(key, (int, slice)): + if is_iterable_like(obj, collections.abc.Sequence): + branching = isinstance(key, slice) + with contextlib.suppress(IndexError): + result = obj[key] + elif traverse_string: + with contextlib.suppress(IndexError): + result = str(obj)[key] + + return branching, result if branching else (result,) + + def lazy_last(iterable): + iterator = iter(iterable) + prev = next(iterator, NO_DEFAULT) + if prev is NO_DEFAULT: + return + + for item in iterator: + yield False, prev + prev = item + + yield True, prev + + def apply_path(start_obj, path, test_type): + objs = (start_obj,) + has_branched = False + + key = None + for last, key in lazy_last(variadic(path, (str, bytes, dict, set))): + if is_user_input and isinstance(key, str): + if key == ':': + key = ... + elif ':' in key: + key = slice(*map(int_or_none, key.split(':'))) + elif int_or_none(key) is not None: + key = int(key) + + if not casesense and isinstance(key, str): + key = key.casefold() + + if __debug__ and callable(key): + # Verify function signature + inspect.signature(key).bind(None, None) + + new_objs = [] + for obj in objs: + branching, results = apply_key(key, obj, last) + has_branched |= branching + new_objs.append(results) + + objs = itertools.chain.from_iterable(new_objs) + + if test_type and not isinstance(key, (dict, list, tuple)): + objs = map(type_test, objs) + + return objs, has_branched, isinstance(key, dict) + + def _traverse_obj(obj, path, allow_empty, test_type): + results, has_branched, is_dict = apply_path(obj, path, test_type) + results = LazyList(item for item in results if item not in (None, {})) + if get_all and has_branched: + if results: + return results.exhaust() + if allow_empty: + return [] if default is NO_DEFAULT else default + return None + + return results[0] if results else {} if allow_empty and is_dict else None + + for index, path in enumerate(paths, 1): + result = _traverse_obj(obj, path, index == len(paths), True) + if result is not None: + return result + + return None if default is NO_DEFAULT else default + + +def get_first(obj, *paths, **kwargs): + return traverse_obj(obj, *((..., *variadic(keys)) for keys in paths), **kwargs, get_all=False) + + +def dict_get(d, key_or_keys, default=None, skip_false_values=True): + for val in map(d.get, variadic(key_or_keys)): + if val is not None and (val or not skip_false_values): + return val + return default |