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[utils] Backport traverse_obj (etc) from yt-dlp (#31156)

* Backport traverse_obj and closely related function from yt-dlp (code by pukkandan)
* Backport LazyList, variadic(), try_call (code by pukkandan)
* Recast using yt-dlp's newer traverse_obj() implementation and tests (code by grub4k)
* Add tests for Unicode case folding support matching Py3.5+ (requires f102e3d)
* Improve/add tests for variadic, try_call, join_nonempty

Co-authored-by: dirkf <>
Andrei Lebedev 3 months ago committed by GitHub
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  1. 323
  2. 339


@ -12,7 +12,9 @@ sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.abspath(__file__)))) @@ -12,7 +12,9 @@ sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
# Various small unit tests
import io
import itertools
import json
import re
import xml.etree.ElementTree
from youtube_dl.utils import (
@ -40,11 +42,14 @@ from youtube_dl.utils import ( @@ -40,11 +42,14 @@ from youtube_dl.utils import (
@ -79,6 +84,8 @@ from youtube_dl.utils import ( @@ -79,6 +84,8 @@ from youtube_dl.utils import (
@ -92,6 +99,7 @@ from youtube_dl.utils import ( @@ -92,6 +99,7 @@ from youtube_dl.utils import (
@ -112,12 +120,18 @@ from youtube_dl.compat import ( @@ -112,12 +120,18 @@ from youtube_dl.compat import (
class TestUtil(unittest.TestCase):
# yt-dlp shim
def assertCountEqual(self, expected, got, msg='count should be the same'):
return self.assertEqual(len(tuple(expected)), len(tuple(got)), msg=msg)
def test_timeconvert(self):
self.assertTrue(timeconvert('') is None)
self.assertTrue(timeconvert('bougrg') is None)
@ -1478,6 +1492,315 @@ Line 1 @@ -1478,6 +1492,315 @@ Line 1
self.assertEqual(clean_podcast_url(''), '')
self.assertEqual(clean_podcast_url(''), '')
def test_LazyList(self):
it = list(range(10))
self.assertEqual(list(LazyList(it)), it)
self.assertEqual(LazyList(it).exhaust(), it)
self.assertEqual(LazyList(it)[5], it[5])
self.assertEqual(LazyList(it)[5:], it[5:])
self.assertEqual(LazyList(it)[:5], it[:5])
self.assertEqual(LazyList(it)[::2], it[::2])
self.assertEqual(LazyList(it)[1::2], it[1::2])
self.assertEqual(LazyList(it)[5::-1], it[5::-1])
self.assertEqual(LazyList(it)[6:2:-2], it[6:2:-2])
self.assertEqual(LazyList(it)[::-1], it[::-1])
self.assertEqual(len(LazyList(it)), len(it))
self.assertEqual(repr(LazyList(it)), repr(it))
self.assertEqual(compat_str(LazyList(it)), compat_str(it))
self.assertEqual(list(LazyList(it, reverse=True)), it[::-1])
self.assertEqual(list(reversed(LazyList(it))[::-1]), it)
self.assertEqual(list(reversed(LazyList(it))[1:3:7]), it[::-1][1:3:7])
def test_LazyList_laziness(self):
def test(ll, idx, val, cache):
self.assertEqual(ll[idx], val)
self.assertEqual(ll._cache, list(cache))
ll = LazyList(range(10))
test(ll, 0, 0, range(1))
test(ll, 5, 5, range(6))
test(ll, -3, 7, range(10))
ll = LazyList(range(10), reverse=True)
test(ll, -1, 0, range(1))
test(ll, 3, 6, range(10))
ll = LazyList(itertools.count())
test(ll, 10, 10, range(11))
ll = reversed(ll)
test(ll, -15, 14, range(15))
def test_try_call(self):
def total(*x, **kwargs):
return sum(x) + sum(kwargs.values())
self.assertEqual(try_call(None), None,
msg='not a fn should give None')
self.assertEqual(try_call(lambda: 1), 1,
msg='int fn with no expected_type should give int')
self.assertEqual(try_call(lambda: 1, expected_type=int), 1,
msg='int fn with expected_type int should give int')
self.assertEqual(try_call(lambda: 1, expected_type=dict), None,
msg='int fn with wrong expected_type should give None')
self.assertEqual(try_call(total, args=(0, 1, 0, ), expected_type=int), 1,
msg='fn should accept arglist')
self.assertEqual(try_call(total, kwargs={'a': 0, 'b': 1, 'c': 0}, expected_type=int), 1,
msg='fn should accept kwargs')
self.assertEqual(try_call(lambda: 1, expected_type=dict), None,
msg='int fn with no expected_type should give None')
self.assertEqual(try_call(lambda x: {}, total, args=(42, ), expected_type=int), 42,
msg='expect first int result with expected_type int')
def test_variadic(self):
self.assertEqual(variadic(None), (None, ))
self.assertEqual(variadic('spam'), ('spam', ))
self.assertEqual(variadic('spam', allowed_types=dict), 'spam')
def test_traverse_obj(self):
100: 100,
1.2: 1.2,
'str': 'str',
'None': None,
'...': Ellipsis,
'urls': [
{'index': 0, 'url': ''},
{'index': 1, 'url': ''},
'data': (
{'index': 2},
{'index': 3},
'dict': {},
# Test base functionality
self.assertEqual(traverse_obj(_TEST_DATA, ('str',)), 'str',
msg='allow tuple path')
self.assertEqual(traverse_obj(_TEST_DATA, ['str']), 'str',
msg='allow list path')
self.assertEqual(traverse_obj(_TEST_DATA, (value for value in ("str",))), 'str',
msg='allow iterable path')
self.assertEqual(traverse_obj(_TEST_DATA, 'str'), 'str',
msg='single items should be treated as a path')
self.assertEqual(traverse_obj(_TEST_DATA, None), _TEST_DATA)
self.assertEqual(traverse_obj(_TEST_DATA, 100), 100)
self.assertEqual(traverse_obj(_TEST_DATA, 1.2), 1.2)
# Test Ellipsis behavior
self.assertCountEqual(traverse_obj(_TEST_DATA, Ellipsis),
(item for item in _TEST_DATA.values() if item is not None),
msg='`...` should give all values except `None`')
self.assertCountEqual(traverse_obj(_TEST_DATA, ('urls', 0, Ellipsis)), _TEST_DATA['urls'][0].values(),
msg='`...` selection for dicts should select all values')
self.assertEqual(traverse_obj(_TEST_DATA, (Ellipsis, Ellipsis, 'url')),
['', ''],
msg='nested `...` queries should work')
self.assertCountEqual(traverse_obj(_TEST_DATA, (Ellipsis, Ellipsis, 'index')), range(4),
msg='`...` query result should be flattened')
# Test function as key
self.assertEqual(traverse_obj(_TEST_DATA, lambda x, y: x == 'urls' and isinstance(y, list)),
msg='function as query key should perform a filter based on (key, value)')
self.assertCountEqual(traverse_obj(_TEST_DATA, lambda _, x: isinstance(x[0], compat_str)), {'str'},
msg='exceptions in the query function should be caught')
# Test alternative paths
self.assertEqual(traverse_obj(_TEST_DATA, 'fail', 'str'), 'str',
msg='multiple `paths` should be treated as alternative paths')
self.assertEqual(traverse_obj(_TEST_DATA, 'str', 100), 'str',
msg='alternatives should exit early')
self.assertEqual(traverse_obj(_TEST_DATA, 'fail', 'fail'), None,
msg='alternatives should return `default` if exhausted')
self.assertEqual(traverse_obj(_TEST_DATA, (Ellipsis, 'fail'), 100), 100,
msg='alternatives should track their own branching return')
self.assertEqual(traverse_obj(_TEST_DATA, ('dict', Ellipsis), ('data', Ellipsis)), list(_TEST_DATA['data']),
msg='alternatives on empty objects should search further')
# Test branch and path nesting
self.assertEqual(traverse_obj(_TEST_DATA, ('urls', (3, 0), 'url')), [''],
msg='tuple as key should be treated as branches')
self.assertEqual(traverse_obj(_TEST_DATA, ('urls', [3, 0], 'url')), [''],
msg='list as key should be treated as branches')
self.assertEqual(traverse_obj(_TEST_DATA, ('urls', ((1, 'fail'), (0, 'url')))), [''],
msg='double nesting in path should be treated as paths')
self.assertEqual(traverse_obj(['0', [1, 2]], [(0, 1), 0]), [1],
msg='do not fail early on branching')
self.assertCountEqual(traverse_obj(_TEST_DATA, ('urls', ((1, ('fail', 'url')), (0, 'url')))),
['', ''],
msg='triple nesting in path should be treated as branches')
self.assertEqual(traverse_obj(_TEST_DATA, ('urls', ('fail', (Ellipsis, 'url')))),
['', ''],
msg='ellipsis as branch path start gets flattened')
# Test dictionary as key
self.assertEqual(traverse_obj(_TEST_DATA, {0: 100, 1: 1.2}), {0: 100, 1: 1.2},
msg='dict key should result in a dict with the same keys')
self.assertEqual(traverse_obj(_TEST_DATA, {0: ('urls', 0, 'url')}),
{0: ''},
msg='dict key should allow paths')
self.assertEqual(traverse_obj(_TEST_DATA, {0: ('urls', (3, 0), 'url')}),
{0: ['']},
msg='tuple in dict path should be treated as branches')
self.assertEqual(traverse_obj(_TEST_DATA, {0: ('urls', ((1, 'fail'), (0, 'url')))}),
{0: ['']},
msg='double nesting in dict path should be treated as paths')
self.assertEqual(traverse_obj(_TEST_DATA, {0: ('urls', ((1, ('fail', 'url')), (0, 'url')))}),
{0: ['', '']},
msg='triple nesting in dict path should be treated as branches')
self.assertEqual(traverse_obj(_TEST_DATA, {0: 'fail'}), {},
msg='remove `None` values when dict key')
self.assertEqual(traverse_obj(_TEST_DATA, {0: 'fail'}, default=Ellipsis), {0: Ellipsis},
msg='do not remove `None` values if `default`')
self.assertEqual(traverse_obj(_TEST_DATA, {0: 'dict'}), {0: {}},
msg='do not remove empty values when dict key')
self.assertEqual(traverse_obj(_TEST_DATA, {0: 'dict'}, default=Ellipsis), {0: {}},
msg='do not remove empty values when dict key and a default')
self.assertEqual(traverse_obj(_TEST_DATA, {0: ('dict', Ellipsis)}), {0: []},
msg='if branch in dict key not successful, return `[]`')
# Testing default parameter behavior
_DEFAULT_DATA = {'None': None, 'int': 0, 'list': []}
self.assertEqual(traverse_obj(_DEFAULT_DATA, 'fail'), None,
msg='default value should be `None`')
self.assertEqual(traverse_obj(_DEFAULT_DATA, 'fail', 'fail', default=Ellipsis), Ellipsis,
msg='chained fails should result in default')
self.assertEqual(traverse_obj(_DEFAULT_DATA, 'None', 'int'), 0,
msg='should not short cirquit on `None`')
self.assertEqual(traverse_obj(_DEFAULT_DATA, 'fail', default=1), 1,
msg='invalid dict key should result in `default`')
self.assertEqual(traverse_obj(_DEFAULT_DATA, 'None', default=1), 1,
msg='`None` is a deliberate sentinel and should become `default`')
self.assertEqual(traverse_obj(_DEFAULT_DATA, ('list', 10)), None,
msg='`IndexError` should result in `default`')
self.assertEqual(traverse_obj(_DEFAULT_DATA, (Ellipsis, 'fail'), default=1), 1,
msg='if branched but not successful return `default` if defined, not `[]`')
self.assertEqual(traverse_obj(_DEFAULT_DATA, (Ellipsis, 'fail'), default=None), None,
msg='if branched but not successful return `default` even if `default` is `None`')
self.assertEqual(traverse_obj(_DEFAULT_DATA, (Ellipsis, 'fail')), [],
msg='if branched but not successful return `[]`, not `default`')
self.assertEqual(traverse_obj(_DEFAULT_DATA, ('list', Ellipsis)), [],
msg='if branched but object is empty return `[]`, not `default`')
# Testing expected_type behavior
_EXPECTED_TYPE_DATA = {'str': 'str', 'int': 0}
self.assertEqual(traverse_obj(_EXPECTED_TYPE_DATA, 'str', expected_type=compat_str), 'str',
msg='accept matching `expected_type` type')
self.assertEqual(traverse_obj(_EXPECTED_TYPE_DATA, 'str', expected_type=int), None,
msg='reject non matching `expected_type` type')
self.assertEqual(traverse_obj(_EXPECTED_TYPE_DATA, 'int', expected_type=lambda x: compat_str(x)), '0',
msg='transform type using type function')
self.assertEqual(traverse_obj(_EXPECTED_TYPE_DATA, 'str',
expected_type=lambda _: 1 / 0), None,
msg='wrap expected_type function in try_call')
self.assertEqual(traverse_obj(_EXPECTED_TYPE_DATA, Ellipsis, expected_type=compat_str), ['str'],
msg='eliminate items that expected_type fails on')
# Test get_all behavior
_GET_ALL_DATA = {'key': [0, 1, 2]}
self.assertEqual(traverse_obj(_GET_ALL_DATA, ('key', Ellipsis), get_all=False), 0,
msg='if not `get_all`, return only first matching value')
self.assertEqual(traverse_obj(_GET_ALL_DATA, Ellipsis, get_all=False), [0, 1, 2],
msg='do not overflatten if not `get_all`')
# Test casesense behavior
'KeY': 'value0',
0: {
'KeY': 'value1',
0: {'KeY': 'value2'},
'\uff2bey': 'value3',
self.assertEqual(traverse_obj(_CASESENSE_DATA, 'key'), None,
msg='dict keys should be case sensitive unless `casesense`')
self.assertEqual(traverse_obj(_CASESENSE_DATA, 'keY',
casesense=False), 'value0',
msg='allow non matching key case if `casesense`')
self.assertEqual(traverse_obj(_CASESENSE_DATA, '\uff4bey', # FULLWIDTH LATIN SMALL LETTER K
casesense=False), 'value3',
msg='allow non matching Unicode key case if `casesense`')
self.assertEqual(traverse_obj(_CASESENSE_DATA, (0, ('keY',)),
casesense=False), ['value1'],
msg='allow non matching key case in branch if `casesense`')
self.assertEqual(traverse_obj(_CASESENSE_DATA, (0, ((0, 'keY'),)),
casesense=False), ['value2'],
msg='allow non matching key case in branch path if `casesense`')
# Test traverse_string behavior
_TRAVERSE_STRING_DATA = {'str': 'str', 1.2: 1.2}
self.assertEqual(traverse_obj(_TRAVERSE_STRING_DATA, ('str', 0)), None,
msg='do not traverse into string if not `traverse_string`')
self.assertEqual(traverse_obj(_TRAVERSE_STRING_DATA, ('str', 0),
_traverse_string=True), 's',
msg='traverse into string if `traverse_string`')
self.assertEqual(traverse_obj(_TRAVERSE_STRING_DATA, (1.2, 1),
_traverse_string=True), '.',
msg='traverse into converted data if `traverse_string`')
self.assertEqual(traverse_obj(_TRAVERSE_STRING_DATA, ('str', Ellipsis),
_traverse_string=True), list('str'),
msg='`...` branching into string should result in list')
self.assertEqual(traverse_obj(_TRAVERSE_STRING_DATA, ('str', (0, 2)),
_traverse_string=True), ['s', 'r'],
msg='branching into string should result in list')
self.assertEqual(traverse_obj(_TRAVERSE_STRING_DATA, ('str', lambda _, x: x),
_traverse_string=True), list('str'),
msg='function branching into string should result in list')
# Test is_user_input behavior
_IS_USER_INPUT_DATA = {'range8': list(range(8))}
self.assertEqual(traverse_obj(_IS_USER_INPUT_DATA, ('range8', '3'),
_is_user_input=True), 3,
msg='allow for string indexing if `is_user_input`')
self.assertCountEqual(traverse_obj(_IS_USER_INPUT_DATA, ('range8', '3:'),
_is_user_input=True), tuple(range(8))[3:],
msg='allow for string slice if `is_user_input`')
self.assertCountEqual(traverse_obj(_IS_USER_INPUT_DATA, ('range8', ':4:2'),
_is_user_input=True), tuple(range(8))[:4:2],
msg='allow step in string slice if `is_user_input`')
self.assertCountEqual(traverse_obj(_IS_USER_INPUT_DATA, ('range8', ':'),
_is_user_input=True), range(8),
msg='`:` should be treated as `...` if `is_user_input`')
with self.assertRaises(TypeError, msg='too many params should result in error'):
traverse_obj(_IS_USER_INPUT_DATA, ('range8', ':::'), _is_user_input=True)
# Test re.Match as input obj
mobj = re.match(r'^0(12)(?P<group>3)(4)?$', '0123')
self.assertEqual(traverse_obj(mobj, Ellipsis), [x for x in mobj.groups() if x is not None],
msg='`...` on a `re.Match` should give its `groups()`')
self.assertEqual(traverse_obj(mobj, lambda k, _: k in (0, 2)), ['0123', '3'],
msg='function on a `re.Match` should give groupno, value starting at 0')
self.assertEqual(traverse_obj(mobj, 'group'), '3',
msg='str key on a `re.Match` should give group with that name')
self.assertEqual(traverse_obj(mobj, 2), '3',
msg='int key on a `re.Match` should give group with that name')
self.assertEqual(traverse_obj(mobj, 'gRoUp', casesense=False), '3',
msg='str key on a `re.Match` should respect casesense')
self.assertEqual(traverse_obj(mobj, 'fail'), None,
msg='failing str key on a `re.Match` should return `default`')
self.assertEqual(traverse_obj(mobj, 'gRoUpS', casesense=False), None,
msg='failing str key on a `re.Match` should return `default`')
self.assertEqual(traverse_obj(mobj, 8), None,
msg='failing int key on a `re.Match` should return `default`')
def test_get_first(self):
self.assertEqual(get_first([{'a': None}, {'a': 'spam'}], 'a'), 'spam')
def test_join_nonempty(self):
self.assertEqual(join_nonempty('a', 'b'), 'a-b')
'a', 'b', 'c', 'd',
from_dict={'a': 'c', 'c': [], 'b': 'd', 'd': None}), 'c-d')
if __name__ == '__main__':


@ -43,6 +43,7 @@ from .compat import ( @@ -43,6 +43,7 @@ from .compat import (
@ -1685,6 +1686,7 @@ USER_AGENTS = { @@ -1685,6 +1686,7 @@ USER_AGENTS = {
NO_DEFAULT = object()
IDENTITY = lambda x: x
'January', 'February', 'March', 'April', 'May', 'June',
@ -3867,6 +3869,105 @@ def detect_exe_version(output, version_re=None, unrecognized='present'): @@ -3867,6 +3869,105 @@ def detect_exe_version(output, version_re=None, unrecognized='present'):
return unrecognized
class LazyList(compat_collections_abc.Sequence):
"""Lazy immutable list from an iterable
Note that slices of a LazyList are lists and not LazyList"""
class IndexError(IndexError):
def __init__(self, cause=None):
if cause:
# reproduce `raise from`
self.__cause__ = cause
super(IndexError, self).__init__()
def __init__(self, iterable, **kwargs):
# kwarg-only
reverse = kwargs.get('reverse', False)
_cache = kwargs.get('_cache')
self._iterable = iter(iterable)
self._cache = [] if _cache is None else _cache
self._reversed = reverse
def __iter__(self):
if self._reversed:
# We need to consume the entire iterable to iterate in reverse
for item in self.exhaust():
yield item
for item in self._cache:
yield item
for item in self._iterable:
yield item
def _exhaust(self):
self._iterable = [] # Discard the emptied iterable to make it pickle-able
return self._cache
def exhaust(self):
"""Evaluate the entire iterable"""
return self._exhaust()[::-1 if self._reversed else 1]
def _reverse_index(x):
return None if x is None else ~x
def __getitem__(self, idx):
if isinstance(idx, slice):
if self._reversed:
idx = slice(self._reverse_index(idx.start), self._reverse_index(idx.stop), -(idx.step or 1))
start, stop, step = idx.start, idx.stop, idx.step or 1
elif isinstance(idx, int):
if self._reversed:
idx = self._reverse_index(idx)
start, stop, step = idx, idx, 0
raise TypeError('indices must be integers or slices')
if ((start or 0) < 0 or (stop or 0) < 0
or (start is None and step < 0)
or (stop is None and step > 0)):
# We need to consume the entire iterable to be able to slice from the end
# Obviously, never use this with infinite iterables
return self._cache[idx]
except IndexError as e:
raise self.IndexError(e)
n = max(start or 0, stop or 0) - len(self._cache) + 1
if n > 0:
self._cache.extend(itertools.islice(self._iterable, n))
return self._cache[idx]
except IndexError as e:
raise self.IndexError(e)
def __bool__(self):
self[-1] if self._reversed else self[0]
except self.IndexError:
return False
return True
def __len__(self):
return len(self._cache)
def __reversed__(self):
return type(self)(self._iterable, reverse=not self._reversed, _cache=self._cache)
def __copy__(self):
return type(self)(self._iterable, reverse=self._reversed, _cache=self._cache)
def __repr__(self):
# repr and str should mimic a list. So we exhaust the iterable
return repr(self.exhaust())
def __str__(self):
return repr(self.exhaust())
class PagedList(object):
def __len__(self):
# This is only useful for tests
@ -4092,6 +4193,10 @@ def multipart_encode(data, boundary=None): @@ -4092,6 +4193,10 @@ def multipart_encode(data, boundary=None):
return out, content_type
def variadic(x, allowed_types=(compat_str, bytes, dict)):
return x if isinstance(x, compat_collections_abc.Iterable) and not isinstance(x, allowed_types) else (x,)
def dict_get(d, key_or_keys, default=None, skip_false_values=True):
if isinstance(key_or_keys, (list, tuple)):
for key in key_or_keys:
@ -4102,6 +4207,23 @@ def dict_get(d, key_or_keys, default=None, skip_false_values=True): @@ -4102,6 +4207,23 @@ def dict_get(d, key_or_keys, default=None, skip_false_values=True):
return d.get(key_or_keys, default)
def try_call(*funcs, **kwargs):
# parameter defaults
expected_type = kwargs.get('expected_type')
fargs = kwargs.get('args', [])
fkwargs = kwargs.get('kwargs', {})
for f in funcs:
val = f(*fargs, **fkwargs)
except (AttributeError, KeyError, TypeError, IndexError, ZeroDivisionError):
if expected_type is None or isinstance(val, expected_type):
return val
def try_get(src, getter, expected_type=None):
if not isinstance(getter, (list, tuple)):
getter = [getter]
@ -5835,3 +5957,220 @@ def clean_podcast_url(url): @@ -5835,3 +5957,220 @@ def clean_podcast_url(url):
st\.fm #
)/''', '', url)
def traverse_obj(obj, *paths, **kwargs):
Safely traverse nested `dict`s and `Sequence`s
>>> obj = [{}, {"key": "value"}]
>>> traverse_obj(obj, (1, "key"))
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`, `Sequence` and `re.Match`.
A value of None is treated as the absence of a value.
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.
- `str`/`int`: Return `obj[key]`. For `re.Match, return ``.
- `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 `Sequence`s, `key` is the index of the value.
- `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.
Keyword arguments:
@param default Value to return if the paths do not match.
@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.
@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.
@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.
A list is always returned if the last path branches and no `default` is given.
# parameter defaults
default = kwargs.get('default', NO_DEFAULT)
expected_type = kwargs.get('expected_type')
get_all = kwargs.get('get_all', True)
casesense = kwargs.get('casesense', True)
_is_user_input = kwargs.get('_is_user_input', False)
_traverse_string = kwargs.get('_traverse_string', False)
# instant compat
str = compat_str
is_sequence = lambda x: isinstance(x, compat_collections_abc.Sequence) and not isinstance(x, (str, bytes))
# stand-in until compat_re_Match is added
compat_re_Match = type(re.match('a', 'a'))
# stand-in until is added
compat_casefold = lambda s: s.casefold()
except AttributeError:
compat_casefold = lambda s: s.lower()
casefold = lambda k: compat_casefold(k) if isinstance(k, str) else k
if isinstance(expected_type, type):
type_test = lambda val: val if isinstance(val, expected_type) else None
type_test = lambda val: try_call(expected_type or IDENTITY, args=(val,))
def from_iterable(iterables):
# chain.from_iterable(['ABC', 'DEF']) --> A B C D E F
for it in iterables:
for item in it:
yield item
def apply_key(key, obj):
if obj is None:
elif key is None:
yield obj
elif isinstance(key, (list, tuple)):
for branch in key:
_, result = apply_path(obj, branch)
for item in result:
yield item
elif key is Ellipsis:
result = []
if isinstance(obj, compat_collections_abc.Mapping):
result = obj.values()
elif is_sequence(obj):
result = obj
elif isinstance(obj, compat_re_Match):
result = obj.groups()
elif _traverse_string:
result = str(obj)
for item in result:
yield item
elif callable(key):
if is_sequence(obj):
iter_obj = enumerate(obj)
elif isinstance(obj, compat_collections_abc.Mapping):
iter_obj = obj.items()
elif isinstance(obj, compat_re_Match):
iter_obj = enumerate(itertools.chain([], obj.groups()))
elif _traverse_string:
iter_obj = enumerate(str(obj))
for item in (v for k, v in iter_obj if try_call(key, args=(k, v))):
yield item
elif isinstance(key, dict):
iter_obj = ((k, _traverse_obj(obj, v)) for k, v in key.items())
yield dict((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)
elif isinstance(obj, compat_collections_abc.Mapping):
yield (obj.get(key) if casesense or (key in obj)
else next((v for k, v in obj.items() if casefold(k) == key), None))
elif isinstance(obj, compat_re_Match):
if isinstance(key, int) or casesense:
except IndexError:
if not isinstance(key, str):
yield next((v for k, v in obj.groupdict().items() if casefold(k) == key), None)
if _is_user_input:
key = (int_or_none(key) if ':' not in key
else slice(*map(int_or_none, key.split(':'))))
if not isinstance(key, (int, slice)):
if not is_sequence(obj):
if not _traverse_string:
obj = str(obj)
yield obj[key]
except IndexError:
def apply_path(start_obj, path):
objs = (start_obj,)
has_branched = False
for key in variadic(path):
if _is_user_input and key == ':':
key = Ellipsis
if not casesense and isinstance(key, str):
key = compat_casefold(key)
if key is Ellipsis or isinstance(key, (list, tuple)) or callable(key):
has_branched = True
key_func = functools.partial(apply_key, key)
objs = from_iterable(map(key_func, objs))
return has_branched, objs
def _traverse_obj(obj, path, use_list=True):
has_branched, results = apply_path(obj, path)
results = LazyList(x for x in map(type_test, results) if x is not None)
if get_all and has_branched:
return results.exhaust() if results or use_list else None
return results[0] if results else None
for index, path in enumerate(paths, 1):
use_list = default is NO_DEFAULT and index == len(paths)
result = _traverse_obj(obj, path, use_list)
if result is not None:
return result
return None if default is NO_DEFAULT else default
def get_first(obj, keys, **kwargs):
return traverse_obj(obj, (Ellipsis,) + tuple(variadic(keys)), get_all=False, **kwargs)
def join_nonempty(*values, **kwargs):
# parameter defaults
delim = kwargs.get('delim', '-')
from_dict = kwargs.get('from_dict')
if from_dict is not None:
values = (traverse_obj(from_dict, variadic(v)) for v in values)
return delim.join(map(compat_str, filter(None, values)))