Datetime API#

NumPy represents dates internally using an int64 counter and a unit metadata struct. Time differences are represented similarly using an int64 and a unit metadata struct. The functions described below are available to to facilitate converting between ISO 8601 date strings, NumPy datetimes, and Python datetime objects in C.

Data types#

In addition to the npy_datetime and npy_timedelta typedefs for npy_int64, NumPy defines two additional structs that represent time unit metadata and an “exploded” view of a datetime.

type PyArray_DatetimeMetaData#

Represents datetime unit metadata.

typedef struct {
    NPY_DATETIMEUNIT base;
    int num;
} PyArray_DatetimeMetaData;
NPY_DATETIMEUNIT base#

The unit of the datetime.

int num#

A multiplier for the unit.

type npy_datetimestruct#

An “exploded” view of a datetime value

typedef struct {
    npy_int64 year;
    npy_int32 month, day, hour, min, sec, us, ps, as;
} npy_datetimestruct;
enum NPY_DATETIMEUNIT#

Time units supported by NumPy. The “FR” in the names of the enum variants is short for frequency.

enumerator NPY_FR_ERROR#

Error or undetermined units.

enumerator NPY_FR_Y#

Years

enumerator NPY_FR_M#

Months

enumerator NPY_FR_W#

Weeks

enumerator NPY_FR_D#

Days

enumerator NPY_FR_h#

Hours

enumerator NPY_FR_m#

Minutes

enumerator NPY_FR_s#

Seconds

enumerator NPY_FR_ms#

Milliseconds

enumerator NPY_FR_us#

Microseconds

enumerator NPY_FR_ns#

Nanoseconds

enumerator NPY_FR_ps#

Picoseconds

enumerator NPY_FR_fs#

Femtoseconds

enumerator NPY_FR_as#

Attoseconds

enumerator NPY_FR_GENERIC#

Unbound units, can convert to anything

Conversion functions#

int NpyDatetime_ConvertDatetimeStructToDatetime64(PyArray_DatetimeMetaData *meta, const npy_datetimestruct *dts, npy_datetime *out)#

Converts a datetime from a datetimestruct to a datetime in the units specified by the unit metadata. The date is assumed to be valid.

If the num member of the metadata struct is large, there may be integer overflow in this function.

Returns 0 on success and -1 on failure.

int NpyDatetime_ConvertDatetime64ToDatetimeStruct(PyArray_DatetimeMetaData *meta, npy_datetime dt, npy_datetimestruct *out)#

Converts a datetime with units specified by the unit metadata to an exploded datetime struct.

Returns 0 on success and -1 on failure.

int NpyDatetime_ConvertPyDateTimeToDatetimeStruct(PyObject *obj, npy_datetimestruct *out, NPY_DATETIMEUNIT *out_bestunit, int apply_tzinfo)#

Tests for and converts a Python datetime.datetime or datetime.date object into a NumPy npy_datetimestruct.

out_bestunit gives a suggested unit based on whether the object was a datetime.date or datetime.datetime object.

If apply_tzinfo is 1, this function uses the tzinfo to convert to UTC time, otherwise it returns the struct with the local time.

Returns -1 on error, 0 on success, and 1 (with no error set) if obj doesn’t have the needed date or datetime attributes.

int NpyDatetime_ParseISO8601Datetime(char const *str, Py_ssize_t len, NPY_DATETIMEUNIT unit, NPY_CASTING casting, npy_datetimestruct *out, NPY_DATETIMEUNIT *out_bestunit, npy_bool *out_special)#

Parses (almost) standard ISO 8601 date strings. The differences are:

  • The date “20100312” is parsed as the year 20100312, not as equivalent to “2010-03-12”. The ‘-’ in the dates are not optional.

  • Only seconds may have a decimal point, with up to 18 digits after it (maximum attoseconds precision).

  • Either a ‘T’ as in ISO 8601 or a ‘ ‘ may be used to separate the date and the time. Both are treated equivalently.

  • Doesn’t (yet) handle the “YYYY-DDD” or “YYYY-Www” formats.

  • Doesn’t handle leap seconds (seconds value has 60 in these cases).

  • Doesn’t handle 24:00:00 as synonym for midnight (00:00:00) tomorrow

  • Accepts special values “NaT” (not a time), “Today”, (current day according to local time) and “Now” (current time in UTC).

str must be a NULL-terminated string, and len must be its length.

unit should contain -1 if the unit is unknown, or the unit which will be used if it is.

casting controls how the detected unit from the string is allowed to be cast to the ‘unit’ parameter.

out gets filled with the parsed date-time.

out_bestunit gives a suggested unit based on the amount of resolution provided in the string, or -1 for NaT.

out_special gets set to 1 if the parsed time was ‘today’, ‘now’, empty string, or ‘NaT’. For ‘today’, the unit recommended is ‘D’, for ‘now’, the unit recommended is ‘s’, and for ‘NaT’ the unit recommended is ‘Y’.

Returns 0 on success, -1 on failure.

int NpyDatetime_GetDatetimeISO8601StrLen(int local, NPY_DATETIMEUNIT base)#

Returns the string length to use for converting datetime objects with the given local time and unit settings to strings. Use this when constructings strings to supply to NpyDatetime_MakeISO8601Datetime.

int NpyDatetime_MakeISO8601Datetime(npy_datetimestruct *dts, char *outstr, npy_intp outlen, int local, int utc, NPY_DATETIMEUNIT base, int tzoffset, NPY_CASTING casting)#

Converts an npy_datetimestruct to an (almost) ISO 8601 NULL-terminated string. If the string fits in the space exactly, it leaves out the NULL terminator and returns success.

The differences from ISO 8601 are the ‘NaT’ string, and the number of year digits is >= 4 instead of strictly 4.

If local is non-zero, it produces a string in local time with a +-#### timezone offset. If local is zero and utc is non-zero, produce a string ending with ‘Z’ to denote UTC. By default, no time zone information is attached.

base restricts the output to that unit. Set base to -1 to auto-detect a base after which all the values are zero.

tzoffset is used if local is enabled, and tzoffset is set to a value other than -1. This is a manual override for the local time zone to use, as an offset in minutes.

casting controls whether data loss is allowed by truncating the data to a coarser unit. This interacts with local, slightly, in order to form a date unit string as a local time, the casting must be unsafe.

Returns 0 on success, -1 on failure (for example if the output string was too short).

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