Source code for pandas.core.tools.datetimes

from __future__ import annotations

from collections import abc
from datetime import datetime
from functools import partial
from itertools import islice
from typing import (
    TYPE_CHECKING,
    Callable,
    Hashable,
    List,
    Tuple,
    TypedDict,
    Union,
    cast,
    overload,
)
import warnings

import numpy as np

from pandas._libs import tslib
from pandas._libs.tslibs import (
    OutOfBoundsDatetime,
    Timedelta,
    Timestamp,
    iNaT,
    nat_strings,
    parsing,
    timezones,
)
from pandas._libs.tslibs.parsing import (
    DateParseError,
    format_is_iso,
    guess_datetime_format,
)
from pandas._libs.tslibs.strptime import array_strptime
from pandas._typing import (
    AnyArrayLike,
    ArrayLike,
    DateTimeErrorChoices,
    Timezone,
    npt,
)
from pandas.util._exceptions import find_stack_level

from pandas.core.dtypes.common import (
    ensure_object,
    is_datetime64_dtype,
    is_datetime64_ns_dtype,
    is_datetime64tz_dtype,
    is_float,
    is_integer,
    is_integer_dtype,
    is_list_like,
    is_numeric_dtype,
    is_scalar,
)
from pandas.core.dtypes.generic import (
    ABCDataFrame,
    ABCSeries,
)
from pandas.core.dtypes.missing import notna

from pandas.arrays import (
    DatetimeArray,
    IntegerArray,
)
from pandas.core import algorithms
from pandas.core.algorithms import unique
from pandas.core.arrays.base import ExtensionArray
from pandas.core.arrays.datetimes import (
    maybe_convert_dtype,
    objects_to_datetime64ns,
    tz_to_dtype,
)
from pandas.core.construction import extract_array
from pandas.core.indexes.base import Index
from pandas.core.indexes.datetimes import DatetimeIndex

if TYPE_CHECKING:
    from pandas._libs.tslibs.nattype import NaTType
    from pandas._libs.tslibs.timedeltas import UnitChoices

    from pandas import (
        DataFrame,
        Series,
    )

# ---------------------------------------------------------------------
# types used in annotations

ArrayConvertible = Union[List, Tuple, AnyArrayLike]
Scalar = Union[float, str]
DatetimeScalar = Union[Scalar, datetime]

DatetimeScalarOrArrayConvertible = Union[DatetimeScalar, ArrayConvertible]

DatetimeDictArg = Union[List[Scalar], Tuple[Scalar, ...], AnyArrayLike]


class YearMonthDayDict(TypedDict, total=True):
    year: DatetimeDictArg
    month: DatetimeDictArg
    day: DatetimeDictArg


class FulldatetimeDict(YearMonthDayDict, total=False):
    hour: DatetimeDictArg
    hours: DatetimeDictArg
    minute: DatetimeDictArg
    minutes: DatetimeDictArg
    second: DatetimeDictArg
    seconds: DatetimeDictArg
    ms: DatetimeDictArg
    us: DatetimeDictArg
    ns: DatetimeDictArg


DictConvertible = Union[FulldatetimeDict, "DataFrame"]
start_caching_at = 50


# ---------------------------------------------------------------------


def _guess_datetime_format_for_array(arr, dayfirst: bool | None = False):
    # Try to guess the format based on the first non-NaN element
    non_nan_elements = notna(arr).nonzero()[0]
    if len(non_nan_elements):
        return guess_datetime_format(arr[non_nan_elements[0]], dayfirst=dayfirst)


def should_cache(
    arg: ArrayConvertible, unique_share: float = 0.7, check_count: int | None = None
) -> bool:
    """
    Decides whether to do caching.

    If the percent of unique elements among `check_count` elements less
    than `unique_share * 100` then we can do caching.

    Parameters
    ----------
    arg: listlike, tuple, 1-d array, Series
    unique_share: float, default=0.7, optional
        0 < unique_share < 1
    check_count: int, optional
        0 <= check_count <= len(arg)

    Returns
    -------
    do_caching: bool

    Notes
    -----
    By default for a sequence of less than 50 items in size, we don't do
    caching; for the number of elements less than 5000, we take ten percent of
    all elements to check for a uniqueness share; if the sequence size is more
    than 5000, then we check only the first 500 elements.
    All constants were chosen empirically by.
    """
    do_caching = True

    # default realization
    if check_count is None:
        # in this case, the gain from caching is negligible
        if len(arg) <= start_caching_at:
            return False

        if len(arg) <= 5000:
            check_count = len(arg) // 10
        else:
            check_count = 500
    else:
        assert (
            0 <= check_count <= len(arg)
        ), "check_count must be in next bounds: [0; len(arg)]"
        if check_count == 0:
            return False

    assert 0 < unique_share < 1, "unique_share must be in next bounds: (0; 1)"

    try:
        # We can't cache if the items are not hashable.
        unique_elements = set(islice(arg, check_count))
    except TypeError:
        return False
    if len(unique_elements) > check_count * unique_share:
        do_caching = False
    return do_caching


def _maybe_cache(
    arg: ArrayConvertible,
    format: str | None,
    cache: bool,
    convert_listlike: Callable,
) -> Series:
    """
    Create a cache of unique dates from an array of dates

    Parameters
    ----------
    arg : listlike, tuple, 1-d array, Series
    format : string
        Strftime format to parse time
    cache : bool
        True attempts to create a cache of converted values
    convert_listlike : function
        Conversion function to apply on dates

    Returns
    -------
    cache_array : Series
        Cache of converted, unique dates. Can be empty
    """
    from pandas import Series

    cache_array = Series(dtype=object)

    if cache:
        # Perform a quicker unique check
        if not should_cache(arg):
            return cache_array

        unique_dates = unique(arg)
        if len(unique_dates) < len(arg):
            cache_dates = convert_listlike(unique_dates, format)
            # GH#45319
            try:
                cache_array = Series(cache_dates, index=unique_dates)
            except OutOfBoundsDatetime:
                return cache_array
            # GH#39882 and GH#35888 in case of None and NaT we get duplicates
            if not cache_array.index.is_unique:
                cache_array = cache_array[~cache_array.index.duplicated()]
    return cache_array


def _box_as_indexlike(
    dt_array: ArrayLike, utc: bool | None = None, name: Hashable = None
) -> Index:
    """
    Properly boxes the ndarray of datetimes to DatetimeIndex
    if it is possible or to generic Index instead

    Parameters
    ----------
    dt_array: 1-d array
        Array of datetimes to be wrapped in an Index.
    tz : object
        None or 'utc'
    name : string, default None
        Name for a resulting index

    Returns
    -------
    result : datetime of converted dates
        - DatetimeIndex if convertible to sole datetime64 type
        - general Index otherwise
    """

    if is_datetime64_dtype(dt_array):
        tz = "utc" if utc else None
        return DatetimeIndex(dt_array, tz=tz, name=name)
    return Index(dt_array, name=name, dtype=dt_array.dtype)


def _convert_and_box_cache(
    arg: DatetimeScalarOrArrayConvertible,
    cache_array: Series,
    name: Hashable | None = None,
) -> Index:
    """
    Convert array of dates with a cache and wrap the result in an Index.

    Parameters
    ----------
    arg : integer, float, string, datetime, list, tuple, 1-d array, Series
    cache_array : Series
        Cache of converted, unique dates
    name : string, default None
        Name for a DatetimeIndex

    Returns
    -------
    result : Index-like of converted dates
    """
    from pandas import Series

    result = Series(arg).map(cache_array)
    return _box_as_indexlike(result._values, utc=None, name=name)


def _return_parsed_timezone_results(result: np.ndarray, timezones, tz, name) -> Index:
    """
    Return results from array_strptime if a %z or %Z directive was passed.

    Parameters
    ----------
    result : ndarray[int64]
        int64 date representations of the dates
    timezones : ndarray
        pytz timezone objects
    tz : object
        None or pytz timezone object
    name : string, default None
        Name for a DatetimeIndex

    Returns
    -------
    tz_result : Index-like of parsed dates with timezone
    """
    tz_results = np.array(
        [Timestamp(res).tz_localize(zone) for res, zone in zip(result, timezones)]
    )
    if tz is not None:
        # Convert to the same tz
        tz_results = np.array([tz_result.tz_convert(tz) for tz_result in tz_results])

    return Index(tz_results, name=name)


def _convert_listlike_datetimes(
    arg,
    format: str | None,
    name: Hashable = None,
    tz: Timezone | None = None,
    unit: str | None = None,
    errors: str = "raise",
    infer_datetime_format: bool = False,
    dayfirst: bool | None = None,
    yearfirst: bool | None = None,
    exact: bool = True,
):
    """
    Helper function for to_datetime. Performs the conversions of 1D listlike
    of dates

    Parameters
    ----------
    arg : list, tuple, ndarray, Series, Index
        date to be parsed
    name : object
        None or string for the Index name
    tz : object
        None or 'utc'
    unit : str
        None or string of the frequency of the passed data
    errors : str
        error handing behaviors from to_datetime, 'raise', 'coerce', 'ignore'
    infer_datetime_format : bool, default False
        inferring format behavior from to_datetime
    dayfirst : bool
        dayfirst parsing behavior from to_datetime
    yearfirst : bool
        yearfirst parsing behavior from to_datetime
    exact : bool, default True
        exact format matching behavior from to_datetime

    Returns
    -------
    Index-like of parsed dates
    """
    if isinstance(arg, (list, tuple)):
        arg = np.array(arg, dtype="O")

    arg_dtype = getattr(arg, "dtype", None)
    # these are shortcutable
    if is_datetime64tz_dtype(arg_dtype):
        if not isinstance(arg, (DatetimeArray, DatetimeIndex)):
            return DatetimeIndex(arg, tz=tz, name=name)
        if tz == "utc":
            arg = arg.tz_convert(None).tz_localize(tz)
        return arg

    elif is_datetime64_ns_dtype(arg_dtype):
        if not isinstance(arg, (DatetimeArray, DatetimeIndex)):
            try:
                return DatetimeIndex(arg, tz=tz, name=name)
            except ValueError:
                pass
        elif tz:
            # DatetimeArray, DatetimeIndex
            return arg.tz_localize(tz)

        return arg

    elif unit is not None:
        if format is not None:
            raise ValueError("cannot specify both format and unit")
        return _to_datetime_with_unit(arg, unit, name, tz, errors)
    elif getattr(arg, "ndim", 1) > 1:
        raise TypeError(
            "arg must be a string, datetime, list, tuple, 1-d array, or Series"
        )

    # warn if passing timedelta64, raise for PeriodDtype
    # NB: this must come after unit transformation
    orig_arg = arg
    try:
        arg, _ = maybe_convert_dtype(arg, copy=False, tz=timezones.maybe_get_tz(tz))
    except TypeError:
        if errors == "coerce":
            npvalues = np.array(["NaT"], dtype="datetime64[ns]").repeat(len(arg))
            return DatetimeIndex(npvalues, name=name)
        elif errors == "ignore":
            idx = Index(arg, name=name)
            return idx
        raise

    arg = ensure_object(arg)
    require_iso8601 = False

    if infer_datetime_format and format is None:
        format = _guess_datetime_format_for_array(arg, dayfirst=dayfirst)

    if format is not None:
        # There is a special fast-path for iso8601 formatted
        # datetime strings, so in those cases don't use the inferred
        # format because this path makes process slower in this
        # special case
        format_is_iso8601 = format_is_iso(format)
        if format_is_iso8601:
            require_iso8601 = not infer_datetime_format
            format = None

    if format is not None:
        res = _to_datetime_with_format(
            arg, orig_arg, name, tz, format, exact, errors, infer_datetime_format
        )
        if res is not None:
            return res

    assert format is None or infer_datetime_format
    utc = tz == "utc"
    result, tz_parsed = objects_to_datetime64ns(
        arg,
        dayfirst=dayfirst,
        yearfirst=yearfirst,
        utc=utc,
        errors=errors,
        require_iso8601=require_iso8601,
        allow_object=True,
    )

    if tz_parsed is not None:
        # We can take a shortcut since the datetime64 numpy array
        # is in UTC
        dta = DatetimeArray(result, dtype=tz_to_dtype(tz_parsed))
        return DatetimeIndex._simple_new(dta, name=name)

    utc = tz == "utc"
    return _box_as_indexlike(result, utc=utc, name=name)


def _array_strptime_with_fallback(
    arg,
    name,
    tz,
    fmt: str,
    exact: bool,
    errors: str,
    infer_datetime_format: bool,
) -> Index | None:
    """
    Call array_strptime, with fallback behavior depending on 'errors'.
    """
    utc = tz == "utc"

    try:
        result, timezones = array_strptime(arg, fmt, exact=exact, errors=errors)
    except OutOfBoundsDatetime:
        if errors == "raise":
            raise
        elif errors == "coerce":
            result = np.empty(arg.shape, dtype="M8[ns]")
            iresult = result.view("i8")
            iresult.fill(iNaT)
        else:
            result = arg
    except ValueError:
        # if fmt was inferred, try falling back
        # to array_to_datetime - terminate here
        # for specified formats
        if not infer_datetime_format:
            if errors == "raise":
                raise
            elif errors == "coerce":
                result = np.empty(arg.shape, dtype="M8[ns]")
                iresult = result.view("i8")
                iresult.fill(iNaT)
            else:
                result = arg
        else:
            # Indicates to the caller to fallback to objects_to_datetime64ns
            return None
    else:
        if "%Z" in fmt or "%z" in fmt:
            return _return_parsed_timezone_results(result, timezones, tz, name)

    return _box_as_indexlike(result, utc=utc, name=name)


def _to_datetime_with_format(
    arg,
    orig_arg,
    name,
    tz,
    fmt: str,
    exact: bool,
    errors: str,
    infer_datetime_format: bool,
) -> Index | None:
    """
    Try parsing with the given format, returning None on failure.
    """
    result = None

    # shortcut formatting here
    if fmt == "%Y%m%d":
        # pass orig_arg as float-dtype may have been converted to
        # datetime64[ns]
        orig_arg = ensure_object(orig_arg)
        try:
            # may return None without raising
            result = _attempt_YYYYMMDD(orig_arg, errors=errors)
        except (ValueError, TypeError, OutOfBoundsDatetime) as err:
            raise ValueError(
                "cannot convert the input to '%Y%m%d' date format"
            ) from err
        if result is not None:
            utc = tz == "utc"
            return _box_as_indexlike(result, utc=utc, name=name)

    # fallback
    res = _array_strptime_with_fallback(
        arg, name, tz, fmt, exact, errors, infer_datetime_format
    )
    return res


def _to_datetime_with_unit(arg, unit, name, tz, errors: str) -> Index:
    """
    to_datetime specalized to the case where a 'unit' is passed.
    """
    arg = extract_array(arg, extract_numpy=True)

    # GH#30050 pass an ndarray to tslib.array_with_unit_to_datetime
    # because it expects an ndarray argument
    if isinstance(arg, IntegerArray):
        arr = arg.astype(f"datetime64[{unit}]")
        tz_parsed = None
    else:
        arg = np.asarray(arg)
        arr, tz_parsed = tslib.array_with_unit_to_datetime(arg, unit, errors=errors)

    if errors == "ignore":
        # Index constructor _may_ infer to DatetimeIndex
        result = Index._with_infer(arr, name=name)
    else:
        result = DatetimeIndex(arr, name=name)

    if not isinstance(result, DatetimeIndex):
        return result

    # GH#23758: We may still need to localize the result with tz
    # GH#25546: Apply tz_parsed first (from arg), then tz (from caller)
    # result will be naive but in UTC
    result = result.tz_localize("UTC").tz_convert(tz_parsed)

    if tz is not None:
        if result.tz is None:
            result = result.tz_localize(tz)
        else:
            result = result.tz_convert(tz)
    return result


def _adjust_to_origin(arg, origin, unit):
    """
    Helper function for to_datetime.
    Adjust input argument to the specified origin

    Parameters
    ----------
    arg : list, tuple, ndarray, Series, Index
        date to be adjusted
    origin : 'julian' or Timestamp
        origin offset for the arg
    unit : str
        passed unit from to_datetime, must be 'D'

    Returns
    -------
    ndarray or scalar of adjusted date(s)
    """
    if origin == "julian":
        original = arg
        j0 = Timestamp(0).to_julian_date()
        if unit != "D":
            raise ValueError("unit must be 'D' for origin='julian'")
        try:
            arg = arg - j0
        except TypeError as err:
            raise ValueError(
                "incompatible 'arg' type for given 'origin'='julian'"
            ) from err

        # preemptively check this for a nice range
        j_max = Timestamp.max.to_julian_date() - j0
        j_min = Timestamp.min.to_julian_date() - j0
        if np.any(arg > j_max) or np.any(arg < j_min):
            raise OutOfBoundsDatetime(
                f"{original} is Out of Bounds for origin='julian'"
            )
    else:
        # arg must be numeric
        if not (
            (is_scalar(arg) and (is_integer(arg) or is_float(arg)))
            or is_numeric_dtype(np.asarray(arg))
        ):
            raise ValueError(
                f"'{arg}' is not compatible with origin='{origin}'; "
                "it must be numeric with a unit specified"
            )

        # we are going to offset back to unix / epoch time
        try:
            offset = Timestamp(origin)
        except OutOfBoundsDatetime as err:
            raise OutOfBoundsDatetime(f"origin {origin} is Out of Bounds") from err
        except ValueError as err:
            raise ValueError(
                f"origin {origin} cannot be converted to a Timestamp"
            ) from err

        if offset.tz is not None:
            raise ValueError(f"origin offset {offset} must be tz-naive")
        td_offset = offset - Timestamp(0)

        # convert the offset to the unit of the arg
        # this should be lossless in terms of precision
        ioffset = td_offset // Timedelta(1, unit=unit)

        # scalars & ndarray-like can handle the addition
        if is_list_like(arg) and not isinstance(arg, (ABCSeries, Index, np.ndarray)):
            arg = np.asarray(arg)
        arg = arg + ioffset
    return arg


@overload
def to_datetime(
    arg: DatetimeScalar,
    errors: DateTimeErrorChoices = ...,
    dayfirst: bool = ...,
    yearfirst: bool = ...,
    utc: bool | None = ...,
    format: str | None = ...,
    exact: bool = ...,
    unit: str | None = ...,
    infer_datetime_format: bool = ...,
    origin=...,
    cache: bool = ...,
) -> Timestamp:
    ...


@overload
def to_datetime(
    arg: Series | DictConvertible,
    errors: DateTimeErrorChoices = ...,
    dayfirst: bool = ...,
    yearfirst: bool = ...,
    utc: bool | None = ...,
    format: str | None = ...,
    exact: bool = ...,
    unit: str | None = ...,
    infer_datetime_format: bool = ...,
    origin=...,
    cache: bool = ...,
) -> Series:
    ...


@overload
def to_datetime(
    arg: list | tuple | Index | ArrayLike,
    errors: DateTimeErrorChoices = ...,
    dayfirst: bool = ...,
    yearfirst: bool = ...,
    utc: bool | None = ...,
    format: str | None = ...,
    exact: bool = ...,
    unit: str | None = ...,
    infer_datetime_format: bool = ...,
    origin=...,
    cache: bool = ...,
) -> DatetimeIndex:
    ...


[docs]def to_datetime( arg: DatetimeScalarOrArrayConvertible | DictConvertible, errors: DateTimeErrorChoices = "raise", dayfirst: bool = False, yearfirst: bool = False, utc: bool | None = None, format: str | None = None, exact: bool = True, unit: str | None = None, infer_datetime_format: bool = False, origin="unix", cache: bool = True, ) -> DatetimeIndex | Series | DatetimeScalar | NaTType | None: """ Convert argument to datetime. This function converts a scalar, array-like, :class:`Series` or :class:`DataFrame`/dict-like to a pandas datetime object. Parameters ---------- arg : int, float, str, datetime, list, tuple, 1-d array, Series, DataFrame/dict-like The object to convert to a datetime. If a :class:`DataFrame` is provided, the method expects minimally the following columns: :const:`"year"`, :const:`"month"`, :const:`"day"`. errors : {'ignore', 'raise', 'coerce'}, default 'raise' - If :const:`'raise'`, then invalid parsing will raise an exception. - If :const:`'coerce'`, then invalid parsing will be set as :const:`NaT`. - If :const:`'ignore'`, then invalid parsing will return the input. dayfirst : bool, default False Specify a date parse order if `arg` is str or is list-like. If :const:`True`, parses dates with the day first, e.g. :const:`"10/11/12"` is parsed as :const:`2012-11-10`. .. warning:: ``dayfirst=True`` is not strict, but will prefer to parse with day first. If a delimited date string cannot be parsed in accordance with the given `dayfirst` option, e.g. ``to_datetime(['31-12-2021'])``, then a warning will be shown. yearfirst : bool, default False Specify a date parse order if `arg` is str or is list-like. - If :const:`True` parses dates with the year first, e.g. :const:`"10/11/12"` is parsed as :const:`2010-11-12`. - If both `dayfirst` and `yearfirst` are :const:`True`, `yearfirst` is preceded (same as :mod:`dateutil`). .. warning:: ``yearfirst=True`` is not strict, but will prefer to parse with year first. utc : bool, default None Control timezone-related parsing, localization and conversion. - If :const:`True`, the function *always* returns a timezone-aware UTC-localized :class:`Timestamp`, :class:`Series` or :class:`DatetimeIndex`. To do this, timezone-naive inputs are *localized* as UTC, while timezone-aware inputs are *converted* to UTC. - If :const:`False` (default), inputs will not be coerced to UTC. Timezone-naive inputs will remain naive, while timezone-aware ones will keep their time offsets. Limitations exist for mixed offsets (typically, daylight savings), see :ref:`Examples <to_datetime_tz_examples>` section for details. See also: pandas general documentation about `timezone conversion and localization <https://pandas.pydata.org/pandas-docs/stable/user_guide/timeseries.html #time-zone-handling>`_. format : str, default None The strftime to parse time, e.g. :const:`"%d/%m/%Y"`. Note that :const:`"%f"` will parse all the way up to nanoseconds. See `strftime documentation <https://docs.python.org/3/library/datetime.html #strftime-and-strptime-behavior>`_ for more information on choices. exact : bool, default True Control how `format` is used: - If :const:`True`, require an exact `format` match. - If :const:`False`, allow the `format` to match anywhere in the target string. unit : str, default 'ns' The unit of the arg (D,s,ms,us,ns) denote the unit, which is an integer or float number. This will be based off the origin. Example, with ``unit='ms'`` and ``origin='unix'``, this would calculate the number of milliseconds to the unix epoch start. infer_datetime_format : bool, default False If :const:`True` and no `format` is given, attempt to infer the format of the datetime strings based on the first non-NaN element, and if it can be inferred, switch to a faster method of parsing them. In some cases this can increase the parsing speed by ~5-10x. origin : scalar, default 'unix' Define the reference date. The numeric values would be parsed as number of units (defined by `unit`) since this reference date. - If :const:`'unix'` (or POSIX) time; origin is set to 1970-01-01. - If :const:`'julian'`, unit must be :const:`'D'`, and origin is set to beginning of Julian Calendar. Julian day number :const:`0` is assigned to the day starting at noon on January 1, 4713 BC. - If Timestamp convertible, origin is set to Timestamp identified by origin. cache : bool, default True If :const:`True`, use a cache of unique, converted dates to apply the datetime conversion. May produce significant speed-up when parsing duplicate date strings, especially ones with timezone offsets. The cache is only used when there are at least 50 values. The presence of out-of-bounds values will render the cache unusable and may slow down parsing. .. versionchanged:: 0.25.0 changed default value from :const:`False` to :const:`True`. Returns ------- datetime If parsing succeeded. Return type depends on input (types in parenthesis correspond to fallback in case of unsuccessful timezone or out-of-range timestamp parsing): - scalar: :class:`Timestamp` (or :class:`datetime.datetime`) - array-like: :class:`DatetimeIndex` (or :class:`Series` with :class:`object` dtype containing :class:`datetime.datetime`) - Series: :class:`Series` of :class:`datetime64` dtype (or :class:`Series` of :class:`object` dtype containing :class:`datetime.datetime`) - DataFrame: :class:`Series` of :class:`datetime64` dtype (or :class:`Series` of :class:`object` dtype containing :class:`datetime.datetime`) Raises ------ ParserError When parsing a date from string fails. ValueError When another datetime conversion error happens. For example when one of 'year', 'month', day' columns is missing in a :class:`DataFrame`, or when a Timezone-aware :class:`datetime.datetime` is found in an array-like of mixed time offsets, and ``utc=False``. See Also -------- DataFrame.astype : Cast argument to a specified dtype. to_timedelta : Convert argument to timedelta. convert_dtypes : Convert dtypes. Notes ----- Many input types are supported, and lead to different output types: - **scalars** can be int, float, str, datetime object (from stdlib :mod:`datetime` module or :mod:`numpy`). They are converted to :class:`Timestamp` when possible, otherwise they are converted to :class:`datetime.datetime`. None/NaN/null scalars are converted to :const:`NaT`. - **array-like** can contain int, float, str, datetime objects. They are converted to :class:`DatetimeIndex` when possible, otherwise they are converted to :class:`Index` with :class:`object` dtype, containing :class:`datetime.datetime`. None/NaN/null entries are converted to :const:`NaT` in both cases. - **Series** are converted to :class:`Series` with :class:`datetime64` dtype when possible, otherwise they are converted to :class:`Series` with :class:`object` dtype, containing :class:`datetime.datetime`. None/NaN/null entries are converted to :const:`NaT` in both cases. - **DataFrame/dict-like** are converted to :class:`Series` with :class:`datetime64` dtype. For each row a datetime is created from assembling the various dataframe columns. Column keys can be common abbreviations like [‘year’, ‘month’, ‘day’, ‘minute’, ‘second’, ‘ms’, ‘us’, ‘ns’]) or plurals of the same. The following causes are responsible for :class:`datetime.datetime` objects being returned (possibly inside an :class:`Index` or a :class:`Series` with :class:`object` dtype) instead of a proper pandas designated type (:class:`Timestamp`, :class:`DatetimeIndex` or :class:`Series` with :class:`datetime64` dtype): - when any input element is before :const:`Timestamp.min` or after :const:`Timestamp.max`, see `timestamp limitations <https://pandas.pydata.org/pandas-docs/stable/user_guide/timeseries.html #timeseries-timestamp-limits>`_. - when ``utc=False`` (default) and the input is an array-like or :class:`Series` containing mixed naive/aware datetime, or aware with mixed time offsets. Note that this happens in the (quite frequent) situation when the timezone has a daylight savings policy. In that case you may wish to use ``utc=True``. Examples -------- **Handling various input formats** Assembling a datetime from multiple columns of a :class:`DataFrame`. The keys can be common abbreviations like ['year', 'month', 'day', 'minute', 'second', 'ms', 'us', 'ns']) or plurals of the same >>> df = pd.DataFrame({'year': [2015, 2016], ... 'month': [2, 3], ... 'day': [4, 5]}) >>> pd.to_datetime(df) 0 2015-02-04 1 2016-03-05 dtype: datetime64[ns] Passing ``infer_datetime_format=True`` can often-times speedup a parsing if its not an ISO8601 format exactly, but in a regular format. >>> s = pd.Series(['3/11/2000', '3/12/2000', '3/13/2000'] * 1000) >>> s.head() 0 3/11/2000 1 3/12/2000 2 3/13/2000 3 3/11/2000 4 3/12/2000 dtype: object >>> %timeit pd.to_datetime(s, infer_datetime_format=True) # doctest: +SKIP 100 loops, best of 3: 10.4 ms per loop >>> %timeit pd.to_datetime(s, infer_datetime_format=False) # doctest: +SKIP 1 loop, best of 3: 471 ms per loop Using a unix epoch time >>> pd.to_datetime(1490195805, unit='s') Timestamp('2017-03-22 15:16:45') >>> pd.to_datetime(1490195805433502912, unit='ns') Timestamp('2017-03-22 15:16:45.433502912') .. warning:: For float arg, precision rounding might happen. To prevent unexpected behavior use a fixed-width exact type. Using a non-unix epoch origin >>> pd.to_datetime([1, 2, 3], unit='D', ... origin=pd.Timestamp('1960-01-01')) DatetimeIndex(['1960-01-02', '1960-01-03', '1960-01-04'], dtype='datetime64[ns]', freq=None) **Non-convertible date/times** If a date does not meet the `timestamp limitations <https://pandas.pydata.org/pandas-docs/stable/user_guide/timeseries.html #timeseries-timestamp-limits>`_, passing ``errors='ignore'`` will return the original input instead of raising any exception. Passing ``errors='coerce'`` will force an out-of-bounds date to :const:`NaT`, in addition to forcing non-dates (or non-parseable dates) to :const:`NaT`. >>> pd.to_datetime('13000101', format='%Y%m%d', errors='ignore') datetime.datetime(1300, 1, 1, 0, 0) >>> pd.to_datetime('13000101', format='%Y%m%d', errors='coerce') NaT .. _to_datetime_tz_examples: **Timezones and time offsets** The default behaviour (``utc=False``) is as follows: - Timezone-naive inputs are converted to timezone-naive :class:`DatetimeIndex`: >>> pd.to_datetime(['2018-10-26 12:00', '2018-10-26 13:00:15']) DatetimeIndex(['2018-10-26 12:00:00', '2018-10-26 13:00:15'], dtype='datetime64[ns]', freq=None) - Timezone-aware inputs *with constant time offset* are converted to timezone-aware :class:`DatetimeIndex`: >>> pd.to_datetime(['2018-10-26 12:00 -0500', '2018-10-26 13:00 -0500']) DatetimeIndex(['2018-10-26 12:00:00-05:00', '2018-10-26 13:00:00-05:00'], dtype='datetime64[ns, pytz.FixedOffset(-300)]', freq=None) - However, timezone-aware inputs *with mixed time offsets* (for example issued from a timezone with daylight savings, such as Europe/Paris) are **not successfully converted** to a :class:`DatetimeIndex`. Instead a simple :class:`Index` containing :class:`datetime.datetime` objects is returned: >>> pd.to_datetime(['2020-10-25 02:00 +0200', '2020-10-25 04:00 +0100']) Index([2020-10-25 02:00:00+02:00, 2020-10-25 04:00:00+01:00], dtype='object') - A mix of timezone-aware and timezone-naive inputs is converted to a timezone-aware :class:`DatetimeIndex` if the offsets of the timezone-aware are constant: >>> from datetime import datetime >>> pd.to_datetime(["2020-01-01 01:00 -01:00", datetime(2020, 1, 1, 3, 0)]) DatetimeIndex(['2020-01-01 01:00:00-01:00', '2020-01-01 02:00:00-01:00'], dtype='datetime64[ns, pytz.FixedOffset(-60)]', freq=None) | Setting ``utc=True`` solves most of the above issues: - Timezone-naive inputs are *localized* as UTC >>> pd.to_datetime(['2018-10-26 12:00', '2018-10-26 13:00'], utc=True) DatetimeIndex(['2018-10-26 12:00:00+00:00', '2018-10-26 13:00:00+00:00'], dtype='datetime64[ns, UTC]', freq=None) - Timezone-aware inputs are *converted* to UTC (the output represents the exact same datetime, but viewed from the UTC time offset `+00:00`). >>> pd.to_datetime(['2018-10-26 12:00 -0530', '2018-10-26 12:00 -0500'], ... utc=True) DatetimeIndex(['2018-10-26 17:30:00+00:00', '2018-10-26 17:00:00+00:00'], dtype='datetime64[ns, UTC]', freq=None) - Inputs can contain both naive and aware, string or datetime, the above rules still apply >>> from datetime import timezone, timedelta >>> pd.to_datetime(['2018-10-26 12:00', '2018-10-26 12:00 -0530', ... datetime(2020, 1, 1, 18), ... datetime(2020, 1, 1, 18, ... tzinfo=timezone(-timedelta(hours=1)))], ... utc=True) DatetimeIndex(['2018-10-26 12:00:00+00:00', '2018-10-26 17:30:00+00:00', '2020-01-01 18:00:00+00:00', '2020-01-01 19:00:00+00:00'], dtype='datetime64[ns, UTC]', freq=None) """ if arg is None: return None if origin != "unix": arg = _adjust_to_origin(arg, origin, unit) tz = "utc" if utc else None convert_listlike = partial( _convert_listlike_datetimes, tz=tz, unit=unit, dayfirst=dayfirst, yearfirst=yearfirst, errors=errors, exact=exact, infer_datetime_format=infer_datetime_format, ) result: Timestamp | NaTType | Series | Index if isinstance(arg, Timestamp): result = arg if tz is not None: if arg.tz is not None: result = arg.tz_convert(tz) else: result = arg.tz_localize(tz) elif isinstance(arg, ABCSeries): cache_array = _maybe_cache(arg, format, cache, convert_listlike) if not cache_array.empty: result = arg.map(cache_array) else: values = convert_listlike(arg._values, format) result = arg._constructor(values, index=arg.index, name=arg.name) elif isinstance(arg, (ABCDataFrame, abc.MutableMapping)): result = _assemble_from_unit_mappings(arg, errors, tz) elif isinstance(arg, Index): cache_array = _maybe_cache(arg, format, cache, convert_listlike) if not cache_array.empty: result = _convert_and_box_cache(arg, cache_array, name=arg.name) else: result = convert_listlike(arg, format, name=arg.name) elif is_list_like(arg): try: # error: Argument 1 to "_maybe_cache" has incompatible type # "Union[float, str, datetime, List[Any], Tuple[Any, ...], ExtensionArray, # ndarray[Any, Any], Series]"; expected "Union[List[Any], Tuple[Any, ...], # Union[Union[ExtensionArray, ndarray[Any, Any]], Index, Series], Series]" argc = cast( Union[list, tuple, ExtensionArray, np.ndarray, "Series", Index], arg ) cache_array = _maybe_cache(argc, format, cache, convert_listlike) except OutOfBoundsDatetime: # caching attempts to create a DatetimeIndex, which may raise # an OOB. If that's the desired behavior, then just reraise... if errors == "raise": raise # ... otherwise, continue without the cache. from pandas import Series cache_array = Series([], dtype=object) # just an empty array if not cache_array.empty: result = _convert_and_box_cache(argc, cache_array) else: result = convert_listlike(argc, format) else: result = convert_listlike(np.array([arg]), format)[0] if isinstance(arg, bool) and isinstance(result, np.bool_): result = bool(result) # TODO: avoid this kludge. # error: Incompatible return value type (got "Union[Timestamp, NaTType, # Series, Index]", expected "Union[DatetimeIndex, Series, float, str, # NaTType, None]") return result # type: ignore[return-value]
# mappings for assembling units _unit_map = { "year": "year", "years": "year", "month": "month", "months": "month", "day": "day", "days": "day", "hour": "h", "hours": "h", "minute": "m", "minutes": "m", "second": "s", "seconds": "s", "ms": "ms", "millisecond": "ms", "milliseconds": "ms", "us": "us", "microsecond": "us", "microseconds": "us", "ns": "ns", "nanosecond": "ns", "nanoseconds": "ns", } def _assemble_from_unit_mappings(arg, errors: DateTimeErrorChoices, tz): """ assemble the unit specified fields from the arg (DataFrame) Return a Series for actual parsing Parameters ---------- arg : DataFrame errors : {'ignore', 'raise', 'coerce'}, default 'raise' - If :const:`'raise'`, then invalid parsing will raise an exception - If :const:`'coerce'`, then invalid parsing will be set as :const:`NaT` - If :const:`'ignore'`, then invalid parsing will return the input tz : None or 'utc' Returns ------- Series """ from pandas import ( DataFrame, to_numeric, to_timedelta, ) arg = DataFrame(arg) if not arg.columns.is_unique: raise ValueError("cannot assemble with duplicate keys") # replace passed unit with _unit_map def f(value): if value in _unit_map: return _unit_map[value] # m is case significant if value.lower() in _unit_map: return _unit_map[value.lower()] return value unit = {k: f(k) for k in arg.keys()} unit_rev = {v: k for k, v in unit.items()} # we require at least Ymd required = ["year", "month", "day"] req = sorted(set(required) - set(unit_rev.keys())) if len(req): _required = ",".join(req) raise ValueError( "to assemble mappings requires at least that " f"[year, month, day] be specified: [{_required}] is missing" ) # keys we don't recognize excess = sorted(set(unit_rev.keys()) - set(_unit_map.values())) if len(excess): _excess = ",".join(excess) raise ValueError( f"extra keys have been passed to the datetime assemblage: [{_excess}]" ) def coerce(values): # we allow coercion to if errors allows values = to_numeric(values, errors=errors) # prevent overflow in case of int8 or int16 if is_integer_dtype(values): values = values.astype("int64", copy=False) return values values = ( coerce(arg[unit_rev["year"]]) * 10000 + coerce(arg[unit_rev["month"]]) * 100 + coerce(arg[unit_rev["day"]]) ) try: values = to_datetime(values, format="%Y%m%d", errors=errors, utc=tz) except (TypeError, ValueError) as err: raise ValueError(f"cannot assemble the datetimes: {err}") from err units: list[UnitChoices] = ["h", "m", "s", "ms", "us", "ns"] for u in units: value = unit_rev.get(u) if value is not None and value in arg: try: values += to_timedelta(coerce(arg[value]), unit=u, errors=errors) except (TypeError, ValueError) as err: raise ValueError( f"cannot assemble the datetimes [{value}]: {err}" ) from err return values def _attempt_YYYYMMDD(arg: npt.NDArray[np.object_], errors: str) -> np.ndarray | None: """ try to parse the YYYYMMDD/%Y%m%d format, try to deal with NaT-like, arg is a passed in as an object dtype, but could really be ints/strings with nan-like/or floats (e.g. with nan) Parameters ---------- arg : np.ndarray[object] errors : {'raise','ignore','coerce'} """ def calc(carg): # calculate the actual result carg = carg.astype(object, copy=False) parsed = parsing.try_parse_year_month_day( carg / 10000, carg / 100 % 100, carg % 100 ) return tslib.array_to_datetime(parsed, errors=errors)[0] def calc_with_mask(carg, mask): result = np.empty(carg.shape, dtype="M8[ns]") iresult = result.view("i8") iresult[~mask] = iNaT masked_result = calc(carg[mask].astype(np.float64).astype(np.int64)) result[mask] = masked_result.astype("M8[ns]") return result # try intlike / strings that are ints try: return calc(arg.astype(np.int64)) except (ValueError, OverflowError, TypeError): pass # a float with actual np.nan try: carg = arg.astype(np.float64) return calc_with_mask(carg, notna(carg)) except (ValueError, OverflowError, TypeError): pass # string with NaN-like try: # error: Argument 2 to "isin" has incompatible type "List[Any]"; expected # "Union[Union[ExtensionArray, ndarray], Index, Series]" mask = ~algorithms.isin(arg, list(nat_strings)) # type: ignore[arg-type] return calc_with_mask(arg, mask) except (ValueError, OverflowError, TypeError): pass return None def to_time(arg, format=None, infer_time_format=False, errors="raise"): # GH#34145 warnings.warn( "`to_time` has been moved, should be imported from pandas.core.tools.times. " "This alias will be removed in a future version.", FutureWarning, stacklevel=find_stack_level(), ) from pandas.core.tools.times import to_time return to_time(arg, format, infer_time_format, errors) __all__ = [ "DateParseError", "should_cache", "to_datetime", "to_time", ]