relationalai.std.dates.datetime.strptime()

datetime.strptime(date_string: str|Producer, format: str|Producer) -> Expression

Constructs a UTC datetime value from date_string, parsed according to format. If date_string and format are Producer objects, then datetime.strptime() also acts as a filter and removes non-string values from the producers. Strings that do not match the format are also filtered out. Must be called in a rule or query context.

Parameters

Name	Type	Description
`date_string`	`str` or `Producer`	The date string to convert to a UTC datetime value.
`format`	`str` or `Producer`	The format string to parse the date string. See Format Codes for supported format codes.

Returns

An Expression object.

Format Codes

The following format codes are supported by datetime.strptime():

Code	Example	Description
`y`	2024	Matches a year.
`m`	1, 01	Matches a 1 or 2-digit month.
`d`	1, 01	Matches a 1 or 2-digit day.
`H`	00	Matches 2-digit hours (24-hour clock)
`I`	00	Matches 2-digit hours (12-hour clock)
`M`	00	Matches 2-digit minutes.
`S`	00	Matches 2-digit seconds.
`s`	.500	Matches 3-digit milliseconds.
`e`	Mon, Tues	Matches abbreviated days of the week.
`E`	Monday, Tuesday	Matches full days of the week.
`p`	AM, am	Matches AM/PM (case-insensitive).
`yyyymmdd`	20240101	Matches fixed-width year, month, and date.
`z`	+04:00, +0400, UTC+4	Matches a numeric UTC offset.
`Z`	Asia/Dubai, UTC	Matches names of time zones in the TZ database.
`u`	Jan	Matches abbreviated months according to the locale.
`U`	January	Matches full months according to the locale.

Common ISO format strings are available in the ISO namespace.

Example

Use datetime.strptime() to construct a UTC datetime value from a date string parsed according to a format string”

import relationalai as rai
from relationalai.std import dates


# =====
# SETUP
# =====

model = rai.Model("MyModel")
Event = model.Type("Event")

with model.rule():
    Event.add(id=1).set(time_str="2021-01-01T09:30:00")
    Event.add(id=2).set(time_str="invalid")


# =======
# EXAMPLE
# =======

with model.rule():
    event = Event()
    # datetime.strptime() filters out any events with invalid time strings, so the
    # following only sets the time property for Event 1.
    event.set(time=dates.datetime.strptime(event.time_str, "y-m-dTH:M:S"))
    # Since Event 2 is filtered out above, the following only sets the
    # has_valid_time_str property for Event 1.
    event.set(has_valid_time_str=True)

with model.query() as select:
    event = Event()
    response = select(event.id, event.time, event.has_valid_time_str)

print(response.results)
#    id                time has_valid_time_str
# 0   1 2021-01-01 09:30:00               True
# 1   2                 NaT                NaN

If a property is assigned to strings with multiple date formats, you can parse them all using a Model.match() block:

with model.rule():
    Event.add(id=3).set(time_str="February 2, 2021 at 02:00 PM")

with model.rule():
    event = Event()
    with model.match():
        with model.case():
            # Set the time property for events with strings in the format "y-m-dTH:M:S".
            event.set(time=dates.datetime.strptime(event.time_str, "y-m-dTH:M:S"))
        with model.case():
            # Set the time property for events with strings in the format "U d, y H:Mp".
            event.set(time=dates.datetime.strptime(event.time_str, "U d, y at I:M p"))

with model.query() as select:
    event = Event()
    response = select(event.id, event.time_str, event.time)

print(response.results)
#    id                      time_str                time
# 0   1           2021-01-01T09:30:00 2021-01-01 09:30:00
# 1   2                       invalid                 NaT
# 2   3  February 2, 2021 at 02:00 PM 2021-02-02 14:00:00

If the string contains a timezone or offset, you can specify it in the format string, but note that the datetime is converted to UTC:

with model.query() as select:
    dt = dates.datetime.strptime("2021-01-01T09:30:00+04:00", "y-m-dTH:M:Sz")
    response = select(dt)

print(response.results)
#                     v
# 0 2021-01-01 05:30:00  <-- 05:30:00 + 4 hours = 09:30:00