sqlglot.helper API documentation

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# sqlglot.helper

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      1from __future__ import annotations
      2
      3import inspect
      4import logging
      5import re
      6import sys
      7import typing as t
      8from collections.abc import Collection
      9from contextlib import contextmanager
     10from copy import copy
     11from enum import Enum
     12
     13if t.TYPE_CHECKING:
     14    from sqlglot import exp
     15    from sqlglot.expressions import Expression
     16
     17    T = t.TypeVar("T")
     18    E = t.TypeVar("E", bound=Expression)
     19
     20CAMEL_CASE_PATTERN = re.compile("(?<!^)(?=[A-Z])")
     21PYTHON_VERSION = sys.version_info[:2]
     22logger = logging.getLogger("sqlglot")
     23
     24
     25class AutoName(Enum):
     26    """This is used for creating enum classes where `auto()` is the string form of the corresponding value's name."""
     27
     28    def _generate_next_value_(name, _start, _count, _last_values):  # type: ignore
     29        return name
     30
     31
     32def seq_get(seq: t.Sequence[T], index: int) -> t.Optional[T]:
     33    """Returns the value in `seq` at position `index`, or `None` if `index` is out of bounds."""
     34    try:
     35        return seq[index]
     36    except IndexError:
     37        return None
     38
     39
     40@t.overload
     41def ensure_list(value: t.Collection[T]) -> t.List[T]:
     42    ...
     43
     44
     45@t.overload
     46def ensure_list(value: T) -> t.List[T]:
     47    ...
     48
     49
     50def ensure_list(value):
     51    """
     52    Ensures that a value is a list, otherwise casts or wraps it into one.
     53
     54    Args:
     55        value: the value of interest.
     56
     57    Returns:
     58        The value cast as a list if it's a list or a tuple, or else the value wrapped in a list.
     59    """
     60    if value is None:
     61        return []
     62    elif isinstance(value, (list, tuple)):
     63        return list(value)
     64
     65    return [value]
     66
     67
     68@t.overload
     69def ensure_collection(value: t.Collection[T]) -> t.Collection[T]:
     70    ...
     71
     72
     73@t.overload
     74def ensure_collection(value: T) -> t.Collection[T]:
     75    ...
     76
     77
     78def ensure_collection(value):
     79    """
     80    Ensures that a value is a collection (excluding `str` and `bytes`), otherwise wraps it into a list.
     81
     82    Args:
     83        value: the value of interest.
     84
     85    Returns:
     86        The value if it's a collection, or else the value wrapped in a list.
     87    """
     88    if value is None:
     89        return []
     90    return (
     91        value if isinstance(value, Collection) and not isinstance(value, (str, bytes)) else [value]
     92    )
     93
     94
     95def csv(*args, sep: str = ", ") -> str:
     96    """
     97    Formats any number of string arguments as CSV.
     98
     99    Args:
    100        args: the string arguments to format.
    101        sep: the argument separator.
    102
    103    Returns:
    104        The arguments formatted as a CSV string.
    105    """
    106    return sep.join(arg for arg in args if arg)
    107
    108
    109def subclasses(
    110    module_name: str,
    111    classes: t.Type | t.Tuple[t.Type, ...],
    112    exclude: t.Type | t.Tuple[t.Type, ...] = (),
    113) -> t.List[t.Type]:
    114    """
    115    Returns all subclasses for a collection of classes, possibly excluding some of them.
    116
    117    Args:
    118        module_name: the name of the module to search for subclasses in.
    119        classes: class(es) we want to find the subclasses of.
    120        exclude: class(es) we want to exclude from the returned list.
    121
    122    Returns:
    123        The target subclasses.
    124    """
    125    return [
    126        obj
    127        for _, obj in inspect.getmembers(
    128            sys.modules[module_name],
    129            lambda obj: inspect.isclass(obj) and issubclass(obj, classes) and obj not in exclude,
    130        )
    131    ]
    132
    133
    134def apply_index_offset(expressions: t.List[t.Optional[E]], offset: int) -> t.List[t.Optional[E]]:
    135    """
    136    Applies an offset to a given integer literal expression.
    137
    138    Args:
    139        expressions: the expression the offset will be applied to, wrapped in a list.
    140        offset: the offset that will be applied.
    141
    142    Returns:
    143        The original expression with the offset applied to it, wrapped in a list. If the provided
    144        `expressions` argument contains more than one expressions, it's returned unaffected.
    145    """
    146    if not offset or len(expressions) != 1:
    147        return expressions
    148
    149    expression = expressions[0]
    150
    151    if expression and expression.is_int:
    152        expression = expression.copy()
    153        logger.warning("Applying array index offset (%s)", offset)
    154        expression.args["this"] = str(int(expression.this) + offset)  # type: ignore
    155        return [expression]
    156
    157    return expressions
    158
    159
    160def camel_to_snake_case(name: str) -> str:
    161    """Converts `name` from camelCase to snake_case and returns the result."""
    162    return CAMEL_CASE_PATTERN.sub("_", name).upper()
    163
    164
    165def while_changing(
    166    expression: t.Optional[Expression], func: t.Callable[[t.Optional[Expression]], E]
    167) -> E:
    168    """
    169    Applies a transformation to a given expression until a fix point is reached.
    170
    171    Args:
    172        expression: the expression to be transformed.
    173        func: the transformation to be applied.
    174
    175    Returns:
    176        The transformed expression.
    177    """
    178    while True:
    179        start = hash(expression)
    180        expression = func(expression)
    181        if start == hash(expression):
    182            break
    183    return expression
    184
    185
    186def tsort(dag: t.Dict[T, t.List[T]]) -> t.List[T]:
    187    """
    188    Sorts a given directed acyclic graph in topological order.
    189
    190    Args:
    191        dag: the graph to be sorted.
    192
    193    Returns:
    194        A list that contains all of the graph's nodes in topological order.
    195    """
    196    result = []
    197
    198    def visit(node: T, visited: t.Set[T]) -> None:
    199        if node in result:
    200            return
    201        if node in visited:
    202            raise ValueError("Cycle error")
    203
    204        visited.add(node)
    205
    206        for dep in dag.get(node, []):
    207            visit(dep, visited)
    208
    209        visited.remove(node)
    210        result.append(node)
    211
    212    for node in dag:
    213        visit(node, set())
    214
    215    return result
    216
    217
    218def open_file(file_name: str) -> t.TextIO:
    219    """Open a file that may be compressed as gzip and return it in universal newline mode."""
    220    with open(file_name, "rb") as f:
    221        gzipped = f.read(2) == b"\x1f\x8b"
    222
    223    if gzipped:
    224        import gzip
    225
    226        return gzip.open(file_name, "rt", newline="")
    227
    228    return open(file_name, encoding="utf-8", newline="")
    229
    230
    231@contextmanager
    232def csv_reader(read_csv: exp.ReadCSV) -> t.Any:
    233    """
    234    Returns a csv reader given the expression `READ_CSV(name, ['delimiter', '|', ...])`.
    235
    236    Args:
    237        read_csv: a `ReadCSV` function call
    238
    239    Yields:
    240        A python csv reader.
    241    """
    242    args = read_csv.expressions
    243    file = open_file(read_csv.name)
    244
    245    delimiter = ","
    246    args = iter(arg.name for arg in args)
    247    for k, v in zip(args, args):
    248        if k == "delimiter":
    249            delimiter = v
    250
    251    try:
    252        import csv as csv_
    253
    254        yield csv_.reader(file, delimiter=delimiter)
    255    finally:
    256        file.close()
    257
    258
    259def find_new_name(taken: t.Collection[str], base: str) -> str:
    260    """
    261    Searches for a new name.
    262
    263    Args:
    264        taken: a collection of taken names.
    265        base: base name to alter.
    266
    267    Returns:
    268        The new, available name.
    269    """
    270    if base not in taken:
    271        return base
    272
    273    i = 2
    274    new = f"{base}_{i}"
    275    while new in taken:
    276        i += 1
    277        new = f"{base}_{i}"
    278
    279    return new
    280
    281
    282def object_to_dict(obj: t.Any, **kwargs) -> t.Dict:
    283    """Returns a dictionary created from an object's attributes."""
    284    return {**{k: copy(v) for k, v in vars(obj).copy().items()}, **kwargs}
    285
    286
    287def split_num_words(
    288    value: str, sep: str, min_num_words: int, fill_from_start: bool = True
    289) -> t.List[t.Optional[str]]:
    290    """
    291    Perform a split on a value and return N words as a result with `None` used for words that don't exist.
    292
    293    Args:
    294        value: the value to be split.
    295        sep: the value to use to split on.
    296        min_num_words: the minimum number of words that are going to be in the result.
    297        fill_from_start: indicates that if `None` values should be inserted at the start or end of the list.
    298
    299    Examples:
    300        >>> split_num_words("db.table", ".", 3)
    301        [None, 'db', 'table']
    302        >>> split_num_words("db.table", ".", 3, fill_from_start=False)
    303        ['db', 'table', None]
    304        >>> split_num_words("db.table", ".", 1)
    305        ['db', 'table']
    306
    307    Returns:
    308        The list of words returned by `split`, possibly augmented by a number of `None` values.
    309    """
    310    words = value.split(sep)
    311    if fill_from_start:
    312        return [None] * (min_num_words - len(words)) + words
    313    return words + [None] * (min_num_words - len(words))
    314
    315
    316def is_iterable(value: t.Any) -> bool:
    317    """
    318    Checks if the value is an iterable, excluding the types `str` and `bytes`.
    319
    320    Examples:
    321        >>> is_iterable([1,2])
    322        True
    323        >>> is_iterable("test")
    324        False
    325
    326    Args:
    327        value: the value to check if it is an iterable.
    328
    329    Returns:
    330        A `bool` value indicating if it is an iterable.
    331    """
    332    return hasattr(value, "__iter__") and not isinstance(value, (str, bytes))
    333
    334
    335def flatten(values: t.Iterable[t.Iterable[t.Any] | t.Any]) -> t.Iterator[t.Any]:
    336    """
    337    Flattens an iterable that can contain both iterable and non-iterable elements. Objects of
    338    type `str` and `bytes` are not regarded as iterables.
    339
    340    Examples:
    341        >>> list(flatten([[1, 2], 3, {4}, (5, "bla")]))
    342        [1, 2, 3, 4, 5, 'bla']
    343        >>> list(flatten([1, 2, 3]))
    344        [1, 2, 3]
    345
    346    Args:
    347        values: the value to be flattened.
    348
    349    Yields:
    350        Non-iterable elements in `values`.
    351    """
    352    for value in values:
    353        if is_iterable(value):
    354            yield from flatten(value)
    355        else:
    356            yield value
    357
    358
    359def count_params(function: t.Callable) -> int:
    360    """
    361    Returns the number of formal parameters expected by a function, without counting "self"
    362    and "cls", in case of instance and class methods, respectively.
    363    """
    364    count = function.__code__.co_argcount
    365    return count - 1 if inspect.ismethod(function) else count
    366
    367
    368def dict_depth(d: t.Dict) -> int:
    369    """
    370    Get the nesting depth of a dictionary.
    371
    372    For example:
    373        >>> dict_depth(None)
    374        0
    375        >>> dict_depth({})
    376        1
    377        >>> dict_depth({"a": "b"})
    378        1
    379        >>> dict_depth({"a": {}})
    380        2
    381        >>> dict_depth({"a": {"b": {}}})
    382        3
    383
    384    Args:
    385        d (dict): dictionary
    386
    387    Returns:
    388        int: depth
    389    """
    390    try:
    391        return 1 + dict_depth(next(iter(d.values())))
    392    except AttributeError:
    393        # d doesn't have attribute "values"
    394        return 0
    395    except StopIteration:
    396        # d.values() returns an empty sequence
    397        return 1
    398
    399
    400def first(it: t.Iterable[T]) -> T:
    401    """Returns the first element from an iterable.
    402
    403    Useful for sets.
    404    """
    405    return next(i for i in it)

class AutoName(enum.Enum): View Source

    26class AutoName(Enum):
    27    """This is used for creating enum classes where `auto()` is the string form of the corresponding value's name."""
    28
    29    def _generate_next_value_(name, _start, _count, _last_values):  # type: ignore
    30        return name

This is used for creating enum classes where `auto()` is the string form of the corresponding value's name.

##### Inherited Members

enum.Enum
  name
  value

def seq_get(seq: Sequence[~T], index: int) -> Optional[~T]: View Source

    33def seq_get(seq: t.Sequence[T], index: int) -> t.Optional[T]:
    34    """Returns the value in `seq` at position `index`, or `None` if `index` is out of bounds."""
    35    try:
    36        return seq[index]
    37    except IndexError:
    38        return None

Returns the value in `seq` at position `index`, or `None` if `index` is out of bounds.

def ensure_list(value): View Source

    51def ensure_list(value):
    52    """
    53    Ensures that a value is a list, otherwise casts or wraps it into one.
    54
    55    Args:
    56        value: the value of interest.
    57
    58    Returns:
    59        The value cast as a list if it's a list or a tuple, or else the value wrapped in a list.
    60    """
    61    if value is None:
    62        return []
    63    elif isinstance(value, (list, tuple)):
    64        return list(value)
    65
    66    return [value]

Ensures that a value is a list, otherwise casts or wraps it into one.

###### Arguments:

- value: the value of interest.

###### Returns:

> The value cast as a list if it's a list or a tuple, or else the value wrapped in a list.

def ensure_collection(value): View Source

    79def ensure_collection(value):
    80    """
    81    Ensures that a value is a collection (excluding `str` and `bytes`), otherwise wraps it into a list.
    82
    83    Args:
    84        value: the value of interest.
    85
    86    Returns:
    87        The value if it's a collection, or else the value wrapped in a list.
    88    """
    89    if value is None:
    90        return []
    91    return (
    92        value if isinstance(value, Collection) and not isinstance(value, (str, bytes)) else [value]
    93    )

Ensures that a value is a collection (excluding `str` and `bytes`), otherwise wraps it into a list.

###### Arguments:

- value: the value of interest.

###### Returns:

> The value if it's a collection, or else the value wrapped in a list.

def csv(*args, sep: str = ', ') -> str: View Source

     96def csv(*args, sep: str = ", ") -> str:
     97    """
     98    Formats any number of string arguments as CSV.
     99
    100    Args:
    101        args: the string arguments to format.
    102        sep: the argument separator.
    103
    104    Returns:
    105        The arguments formatted as a CSV string.
    106    """
    107    return sep.join(arg for arg in args if arg)

Formats any number of string arguments as CSV.

###### Arguments:

- args: the string arguments to format.
- sep: the argument separator.

###### Returns:

> The arguments formatted as a CSV string.

def subclasses( module_name: str, classes: Union[Type, Tuple[Type, ...]], exclude: Union[Type, Tuple[Type, ...]] = ()) -> List[Type]: View Source

    110def subclasses(
    111    module_name: str,
    112    classes: t.Type | t.Tuple[t.Type, ...],
    113    exclude: t.Type | t.Tuple[t.Type, ...] = (),
    114) -> t.List[t.Type]:
    115    """
    116    Returns all subclasses for a collection of classes, possibly excluding some of them.
    117
    118    Args:
    119        module_name: the name of the module to search for subclasses in.
    120        classes: class(es) we want to find the subclasses of.
    121        exclude: class(es) we want to exclude from the returned list.
    122
    123    Returns:
    124        The target subclasses.
    125    """
    126    return [
    127        obj
    128        for _, obj in inspect.getmembers(
    129            sys.modules[module_name],
    130            lambda obj: inspect.isclass(obj) and issubclass(obj, classes) and obj not in exclude,
    131        )
    132    ]

Returns all subclasses for a collection of classes, possibly excluding some of them.

###### Arguments:

- module_name: the name of the module to search for subclasses in.
- classes: class(es) we want to find the subclasses of.
- exclude: class(es) we want to exclude from the returned list.

###### Returns:

> The target subclasses.

def apply_index_offset(expressions: List[Optional[~E]], offset: int) -> List[Optional[~E]]: View Source

    135def apply_index_offset(expressions: t.List[t.Optional[E]], offset: int) -> t.List[t.Optional[E]]:
    136    """
    137    Applies an offset to a given integer literal expression.
    138
    139    Args:
    140        expressions: the expression the offset will be applied to, wrapped in a list.
    141        offset: the offset that will be applied.
    142
    143    Returns:
    144        The original expression with the offset applied to it, wrapped in a list. If the provided
    145        `expressions` argument contains more than one expressions, it's returned unaffected.
    146    """
    147    if not offset or len(expressions) != 1:
    148        return expressions
    149
    150    expression = expressions[0]
    151
    152    if expression and expression.is_int:
    153        expression = expression.copy()
    154        logger.warning("Applying array index offset (%s)", offset)
    155        expression.args["this"] = str(int(expression.this) + offset)  # type: ignore
    156        return [expression]
    157
    158    return expressions

Applies an offset to a given integer literal expression.

###### Arguments:

- expressions: the expression the offset will be applied to, wrapped in a list.
- offset: the offset that will be applied.

###### Returns:

> The original expression with the offset applied to it, wrapped in a list. If the provided `expressions` argument contains more than one expressions, it's returned unaffected.

def camel_to_snake_case(name: str) -> str: View Source

    161def camel_to_snake_case(name: str) -> str:
    162    """Converts `name` from camelCase to snake_case and returns the result."""
    163    return CAMEL_CASE_PATTERN.sub("_", name).upper()

Converts `name` from camelCase to snake_case and returns the result.

def while_changing( expression: Optional[sqlglot.expressions.Expression], func: Callable[[Optional[sqlglot.expressions.Expression]], ~E]) -> ~E: View Source

    166def while_changing(
    167    expression: t.Optional[Expression], func: t.Callable[[t.Optional[Expression]], E]
    168) -> E:
    169    """
    170    Applies a transformation to a given expression until a fix point is reached.
    171
    172    Args:
    173        expression: the expression to be transformed.
    174        func: the transformation to be applied.
    175
    176    Returns:
    177        The transformed expression.
    178    """
    179    while True:
    180        start = hash(expression)
    181        expression = func(expression)
    182        if start == hash(expression):
    183            break
    184    return expression

Applies a transformation to a given expression until a fix point is reached.

###### Arguments:

- expression: the expression to be transformed.
- func: the transformation to be applied.

###### Returns:

> The transformed expression.

def tsort(dag: Dict[~T, List[~T]]) -> List[~T]: View Source

    187def tsort(dag: t.Dict[T, t.List[T]]) -> t.List[T]:
    188    """
    189    Sorts a given directed acyclic graph in topological order.
    190
    191    Args:
    192        dag: the graph to be sorted.
    193
    194    Returns:
    195        A list that contains all of the graph's nodes in topological order.
    196    """
    197    result = []
    198
    199    def visit(node: T, visited: t.Set[T]) -> None:
    200        if node in result:
    201            return
    202        if node in visited:
    203            raise ValueError("Cycle error")
    204
    205        visited.add(node)
    206
    207        for dep in dag.get(node, []):
    208            visit(dep, visited)
    209
    210        visited.remove(node)
    211        result.append(node)
    212
    213    for node in dag:
    214        visit(node, set())
    215
    216    return result

Sorts a given directed acyclic graph in topological order.

###### Arguments:

- dag: the graph to be sorted.

###### Returns:

> A list that contains all of the graph's nodes in topological order.

def open_file(file_name: str) -> <class 'TextIO'>: View Source

    219def open_file(file_name: str) -> t.TextIO:
    220    """Open a file that may be compressed as gzip and return it in universal newline mode."""
    221    with open(file_name, "rb") as f:
    222        gzipped = f.read(2) == b"\x1f\x8b"
    223
    224    if gzipped:
    225        import gzip
    226
    227        return gzip.open(file_name, "rt", newline="")
    228
    229    return open(file_name, encoding="utf-8", newline="")

Open a file that may be compressed as gzip and return it in universal newline mode.

@contextmanager
def csv_reader(read_csv: sqlglot.expressions.ReadCSV) -> Any: View Source

    232@contextmanager
    233def csv_reader(read_csv: exp.ReadCSV) -> t.Any:
    234    """
    235    Returns a csv reader given the expression `READ_CSV(name, ['delimiter', '|', ...])`.
    236
    237    Args:
    238        read_csv: a `ReadCSV` function call
    239
    240    Yields:
    241        A python csv reader.
    242    """
    243    args = read_csv.expressions
    244    file = open_file(read_csv.name)
    245
    246    delimiter = ","
    247    args = iter(arg.name for arg in args)
    248    for k, v in zip(args, args):
    249        if k == "delimiter":
    250            delimiter = v
    251
    252    try:
    253        import csv as csv_
    254
    255        yield csv_.reader(file, delimiter=delimiter)
    256    finally:
    257        file.close()

Returns a csv reader given the expression `READ_CSV(name, ['delimiter', '|', ...])`.

###### Arguments:

- read_csv: a `ReadCSV` function call

###### Yields:

> A python csv reader.

def find_new_name(taken: Collection[str], base: str) -> str: View Source

    260def find_new_name(taken: t.Collection[str], base: str) -> str:
    261    """
    262    Searches for a new name.
    263
    264    Args:
    265        taken: a collection of taken names.
    266        base: base name to alter.
    267
    268    Returns:
    269        The new, available name.
    270    """
    271    if base not in taken:
    272        return base
    273
    274    i = 2
    275    new = f"{base}_{i}"
    276    while new in taken:
    277        i += 1
    278        new = f"{base}_{i}"
    279
    280    return new

Searches for a new name.

###### Arguments:

- taken: a collection of taken names.
- base: base name to alter.

###### Returns:

> The new, available name.

def object_to_dict(obj: Any, **kwargs) -> Dict: View Source

    283def object_to_dict(obj: t.Any, **kwargs) -> t.Dict:
    284    """Returns a dictionary created from an object's attributes."""
    285    return {**{k: copy(v) for k, v in vars(obj).copy().items()}, **kwargs}

Returns a dictionary created from an object's attributes.

def split_num_words( value: str, sep: str, min_num_words: int, fill_from_start: bool = True) -> List[Optional[str]]: View Source

    288def split_num_words(
    289    value: str, sep: str, min_num_words: int, fill_from_start: bool = True
    290) -> t.List[t.Optional[str]]:
    291    """
    292    Perform a split on a value and return N words as a result with `None` used for words that don't exist.
    293
    294    Args:
    295        value: the value to be split.
    296        sep: the value to use to split on.
    297        min_num_words: the minimum number of words that are going to be in the result.
    298        fill_from_start: indicates that if `None` values should be inserted at the start or end of the list.
    299
    300    Examples:
    301        >>> split_num_words("db.table", ".", 3)
    302        [None, 'db', 'table']
    303        >>> split_num_words("db.table", ".", 3, fill_from_start=False)
    304        ['db', 'table', None]
    305        >>> split_num_words("db.table", ".", 1)
    306        ['db', 'table']
    307
    308    Returns:
    309        The list of words returned by `split`, possibly augmented by a number of `None` values.
    310    """
    311    words = value.split(sep)
    312    if fill_from_start:
    313        return [None] * (min_num_words - len(words)) + words
    314    return words + [None] * (min_num_words - len(words))

Perform a split on a value and return N words as a result with `None` used for words that don't exist.

###### Arguments:

- value: the value to be split.
- sep: the value to use to split on.
- min_num_words: the minimum number of words that are going to be in the result.
- fill_from_start: indicates that if `None` values should be inserted at the start or end of the list.

###### Examples:

>     >>> split_num_words("db.table", ".", 3)
>     [None, 'db', 'table']
>     >>> split_num_words("db.table", ".", 3, fill_from_start=False)
>     ['db', 'table', None]
>     >>> split_num_words("db.table", ".", 1)
>     ['db', 'table']

###### Returns:

> The list of words returned by `split`, possibly augmented by a number of `None` values.

def is_iterable(value: Any) -> bool: View Source

    317def is_iterable(value: t.Any) -> bool:
    318    """
    319    Checks if the value is an iterable, excluding the types `str` and `bytes`.
    320
    321    Examples:
    322        >>> is_iterable([1,2])
    323        True
    324        >>> is_iterable("test")
    325        False
    326
    327    Args:
    328        value: the value to check if it is an iterable.
    329
    330    Returns:
    331        A `bool` value indicating if it is an iterable.
    332    """
    333    return hasattr(value, "__iter__") and not isinstance(value, (str, bytes))

Checks if the value is an iterable, excluding the types `str` and `bytes`.

###### Examples:

>     >>> is_iterable([1,2])
>     True
>     >>> is_iterable("test")
>     False

###### Arguments:

- value: the value to check if it is an iterable.

###### Returns:

> A `bool` value indicating if it is an iterable.

def flatten(values: Iterable[Union[Iterable[Any], Any]]) -> Iterator[Any]: View Source

    336def flatten(values: t.Iterable[t.Iterable[t.Any] | t.Any]) -> t.Iterator[t.Any]:
    337    """
    338    Flattens an iterable that can contain both iterable and non-iterable elements. Objects of
    339    type `str` and `bytes` are not regarded as iterables.
    340
    341    Examples:
    342        >>> list(flatten([[1, 2], 3, {4}, (5, "bla")]))
    343        [1, 2, 3, 4, 5, 'bla']
    344        >>> list(flatten([1, 2, 3]))
    345        [1, 2, 3]
    346
    347    Args:
    348        values: the value to be flattened.
    349
    350    Yields:
    351        Non-iterable elements in `values`.
    352    """
    353    for value in values:
    354        if is_iterable(value):
    355            yield from flatten(value)
    356        else:
    357            yield value

Flattens an iterable that can contain both iterable and non-iterable elements. Objects of type `str` and `bytes` are not regarded as iterables.

###### Examples:

>     >>> list(flatten([[1, 2], 3, {4}, (5, "bla")]))
>     [1, 2, 3, 4, 5, 'bla']
>     >>> list(flatten([1, 2, 3]))
>     [1, 2, 3]

###### Arguments:

- values: the value to be flattened.

###### Yields:

> Non-iterable elements in `values`.

def count_params(function: Callable) -> int: View Source

    360def count_params(function: t.Callable) -> int:
    361    """
    362    Returns the number of formal parameters expected by a function, without counting "self"
    363    and "cls", in case of instance and class methods, respectively.
    364    """
    365    count = function.__code__.co_argcount
    366    return count - 1 if inspect.ismethod(function) else count

Returns the number of formal parameters expected by a function, without counting "self" and "cls", in case of instance and class methods, respectively.

def dict_depth(d: Dict) -> int: View Source

    369def dict_depth(d: t.Dict) -> int:
    370    """
    371    Get the nesting depth of a dictionary.
    372
    373    For example:
    374        >>> dict_depth(None)
    375        0
    376        >>> dict_depth({})
    377        1
    378        >>> dict_depth({"a": "b"})
    379        1
    380        >>> dict_depth({"a": {}})
    381        2
    382        >>> dict_depth({"a": {"b": {}}})
    383        3
    384
    385    Args:
    386        d (dict): dictionary
    387
    388    Returns:
    389        int: depth
    390    """
    391    try:
    392        return 1 + dict_depth(next(iter(d.values())))
    393    except AttributeError:
    394        # d doesn't have attribute "values"
    395        return 0
    396    except StopIteration:
    397        # d.values() returns an empty sequence
    398        return 1

Get the nesting depth of a dictionary.

###### For example:

>     >>> dict_depth(None)
>     0
>     >>> dict_depth({})
>     1
>     >>> dict_depth({"a": "b"})
>     1
>     >>> dict_depth({"a": {}})
>     2
>     >>> dict_depth({"a": {"b": {}}})
>     3

###### Arguments:

- d (dict): dictionary

###### Returns:

> int: depth

def first(it: Iterable[~T]) -> ~T: View Source

    401def first(it: t.Iterable[T]) -> T:
    402    """Returns the first element from an iterable.
    403
    404    Useful for sets.
    405    """
    406    return next(i for i in it)

Returns the first element from an iterable.

Useful for sets.