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relationalai.std.dates.days()

days(n: int|Producer) -> Expression

Creates a period of n days. Negative values are supported. If n is a Producer object, then days() also acts as a filter and removes non-integer values from the producer. Must be called in a rule or query context.

Parameters

Name	Type	Description
`n`	`Producer` or Python `int`	The number of days.

Returns

An Expression object.

Example

Use days() to create a period of n days. You can add and subtract time periods from date or datetime values using the + and - operators:

import relationalai as rai
from relationalai.std import alias, dates


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

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

with model.rule():
    Event.add(id=1).set(start=dates.date(2021, 1, 1), duration_days=1)
    Event.add(id=2).set(start=dates.datetime(2021, 2, 1, 9, 30), duration_days=2)
    Event.add(id=3).set(start=dates.date(2021, 3, 1), duration_days=-1)
    Event.add(id=4).set(start=dates.date(2021, 4, 1), duration_days="invalid")


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

with model.rule():
    event = Event()
    # days() filters out any events with invalid duration_days, so the following
    # only sets the end property for Events 1, 2, and 3.
    event.set(end=event.start + dates.days(event.duration_days))
    # Since Event 4 is filtered out above, the following only sets the
    # has_valid_duration property for Events 1, 2, and 3.
    event.set(has_valid_duration=True)

with model.query() as select:
    event = Event()
    response = select(event.id, event.end, event.has_valid_duration)

print(response.results)
#    id                 end has_valid_duration
# 0   1 2021-01-02 00:00:00               True
# 1   2 2021-02-03 09:30:00               True
# 2   3 2021-02-28 00:00:00               True
# 3   4                 NaT                NaN

Note that days() does not produce an integer value. In particular, you cannot do arithmetic with days() and numeric values:

with model.query() as select:
    result = dates.days(2) / 365
    response = select(result)

# Returns an empty result set because `days(2) / 365` is not a valid expression.
print(response.results)
# Empty DataFrame
# Columns: []
# Index: []

See Also