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Merged
kosiew merged 5 commits into from
Mar 18, 2026
Merged

Add docstring examples for Scalar temporal functions #1424

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435d82a
Add docstring examples for Scalar temporal functions
ntjohnson1 Mar 5, 2026
b517838
Remove examples for aliases
ntjohnson1 Mar 14, 2026
00ac681
Fix claude's attempt to cheat with sql
ntjohnson1 Mar 14, 2026
4628f9e
Make examples follow google docstyle
ntjohnson1 Mar 14, 2026
9457274
Merge branch 'main' of github.com:apache/datafusion-python into nick/…
ntjohnson1 Mar 17, 2026
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178 changes: 170 additions & 8 deletions python/datafusion/functions.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1562,6 +1562,19 @@ def now() -> Expr:
"""Returns the current timestamp in nanoseconds.

This will use the same value for all instances of now() in same statement.

Examples:
>>> ctx = dfn.SessionContext()
>>> df = ctx.from_pydict({"a": [1]})
>>> result = df.select(
... dfn.functions.now().alias("now")
... )

Use .value instead of .as_py() because nanosecond timestamps
require pandas to convert to Python datetime objects.

>>> result.collect_column("now")[0].value > 0
True
"""
return Expr(f.now())

Expand Down Expand Up @@ -1622,6 +1635,17 @@ def to_timestamp(arg: Expr, *formatters: Expr) -> Expr:
For usage of ``formatters`` see the rust chrono package ``strftime`` package.

[Documentation here.](https://docs.rs/chrono/latest/chrono/format/strftime/index.html)

Examples:
>>> ctx = dfn.SessionContext()
>>> df = ctx.from_pydict({"a": ["2021-01-01T00:00:00"]})
>>> result = df.select(
... dfn.functions.to_timestamp(
... dfn.col("a")
... ).alias("ts")
... )
>>> str(result.collect_column("ts")[0].as_py())
'2021-01-01 00:00:00'
"""
return Expr(f.to_timestamp(arg.expr, *_unwrap_exprs(formatters)))

Expand All @@ -1630,6 +1654,17 @@ def to_timestamp_millis(arg: Expr, *formatters: Expr) -> Expr:
"""Converts a string and optional formats to a ``Timestamp`` in milliseconds.

See :py:func:`to_timestamp` for a description on how to use formatters.

Examples:
>>> ctx = dfn.SessionContext()
>>> df = ctx.from_pydict({"a": ["2021-01-01T00:00:00"]})
>>> result = df.select(
... dfn.functions.to_timestamp_millis(
... dfn.col("a")
... ).alias("ts")
... )
>>> str(result.collect_column("ts")[0].as_py())
'2021-01-01 00:00:00'
"""
return Expr(f.to_timestamp_millis(arg.expr, *_unwrap_exprs(formatters)))

Expand All @@ -1638,6 +1673,17 @@ def to_timestamp_micros(arg: Expr, *formatters: Expr) -> Expr:
"""Converts a string and optional formats to a ``Timestamp`` in microseconds.

See :py:func:`to_timestamp` for a description on how to use formatters.

Examples:
>>> ctx = dfn.SessionContext()
>>> df = ctx.from_pydict({"a": ["2021-01-01T00:00:00"]})
>>> result = df.select(
... dfn.functions.to_timestamp_micros(
... dfn.col("a")
... ).alias("ts")
... )
>>> str(result.collect_column("ts")[0].as_py())
'2021-01-01 00:00:00'
"""
return Expr(f.to_timestamp_micros(arg.expr, *_unwrap_exprs(formatters)))

Expand All @@ -1646,6 +1692,17 @@ def to_timestamp_nanos(arg: Expr, *formatters: Expr) -> Expr:
"""Converts a string and optional formats to a ``Timestamp`` in nanoseconds.

See :py:func:`to_timestamp` for a description on how to use formatters.

Examples:
>>> ctx = dfn.SessionContext()
>>> df = ctx.from_pydict({"a": ["2021-01-01T00:00:00"]})
>>> result = df.select(
... dfn.functions.to_timestamp_nanos(
... dfn.col("a")
... ).alias("ts")
... )
>>> str(result.collect_column("ts")[0].as_py())
'2021-01-01 00:00:00'
"""
return Expr(f.to_timestamp_nanos(arg.expr, *_unwrap_exprs(formatters)))

Expand All @@ -1654,25 +1711,68 @@ def to_timestamp_seconds(arg: Expr, *formatters: Expr) -> Expr:
"""Converts a string and optional formats to a ``Timestamp`` in seconds.

See :py:func:`to_timestamp` for a description on how to use formatters.

Examples:
>>> ctx = dfn.SessionContext()
>>> df = ctx.from_pydict({"a": ["2021-01-01T00:00:00"]})
>>> result = df.select(
... dfn.functions.to_timestamp_seconds(
... dfn.col("a")
... ).alias("ts")
... )
>>> str(result.collect_column("ts")[0].as_py())
'2021-01-01 00:00:00'
"""
return Expr(f.to_timestamp_seconds(arg.expr, *_unwrap_exprs(formatters)))


def to_unixtime(string: Expr, *format_arguments: Expr) -> Expr:
"""Converts a string and optional formats to a Unixtime."""
"""Converts a string and optional formats to a Unixtime.

Examples:
>>> ctx = dfn.SessionContext()
>>> df = ctx.from_pydict({"a": ["1970-01-01T00:00:00"]})
>>> result = df.select(dfn.functions.to_unixtime(dfn.col("a")).alias("u"))
>>> result.collect_column("u")[0].as_py()
0
"""
return Expr(f.to_unixtime(string.expr, *_unwrap_exprs(format_arguments)))


def current_date() -> Expr:
"""Returns current UTC date as a Date32 value."""
"""Returns current UTC date as a Date32 value.

Examples:
>>> ctx = dfn.SessionContext()
>>> df = ctx.from_pydict({"a": [1]})
>>> result = df.select(
... dfn.functions.current_date().alias("d")
... )
>>> result.collect_column("d")[0].as_py() is not None
True
"""
return Expr(f.current_date())


today = current_date


def current_time() -> Expr:
"""Returns current UTC time as a Time64 value."""
"""Returns current UTC time as a Time64 value.

Examples:
>>> ctx = dfn.SessionContext()
>>> df = ctx.from_pydict({"a": [1]})
>>> result = df.select(
... dfn.functions.current_time().alias("t")
... )

Use .value instead of .as_py() because nanosecond timestamps
require pandas to convert to Python datetime objects.

>>> result.collect_column("t")[0].value > 0
True
"""
return Expr(f.current_time())


Expand All @@ -1685,7 +1785,17 @@ def datepart(part: Expr, date: Expr) -> Expr:


def date_part(part: Expr, date: Expr) -> Expr:
"""Extracts a subfield from the date."""
"""Extracts a subfield from the date.

Examples:
>>> ctx = dfn.SessionContext()
>>> df = ctx.from_pydict({"a": ["2021-07-15T00:00:00"]})
>>> df = df.select(dfn.functions.to_timestamp(dfn.col("a")).alias("a"))
>>> result = df.select(
... dfn.functions.date_part(dfn.lit("year"), dfn.col("a")).alias("y"))
>>> result.collect_column("y")[0].as_py()
2021
"""
return Expr(f.date_part(part.expr, date.expr))


Expand All @@ -1698,7 +1808,20 @@ def extract(part: Expr, date: Expr) -> Expr:


def date_trunc(part: Expr, date: Expr) -> Expr:
"""Truncates the date to a specified level of precision."""
"""Truncates the date to a specified level of precision.

Examples:
>>> ctx = dfn.SessionContext()
>>> df = ctx.from_pydict({"a": ["2021-07-15T12:34:56"]})
>>> df = df.select(dfn.functions.to_timestamp(dfn.col("a")).alias("a"))
>>> result = df.select(
... dfn.functions.date_trunc(
... dfn.lit("month"), dfn.col("a")
... ).alias("t")
... )
>>> str(result.collect_column("t")[0].as_py())
'2021-07-01 00:00:00'
"""
return Expr(f.date_trunc(part.expr, date.expr))


Expand All @@ -1711,12 +1834,39 @@ def datetrunc(part: Expr, date: Expr) -> Expr:


def date_bin(stride: Expr, source: Expr, origin: Expr) -> Expr:
"""Coerces an arbitrary timestamp to the start of the nearest specified interval."""
"""Coerces an arbitrary timestamp to the start of the nearest specified interval.

Examples:
>>> ctx = dfn.SessionContext()
>>> df = ctx.from_pydict({"timestamp": ['2021-07-15 12:34:56', '2021-01-01']})
>>> result = df.select(
... dfn.functions.date_bin(
... dfn.string_literal("15 minutes"),
... dfn.col("timestamp"),
... dfn.string_literal("2001-01-01 00:00:00")
... ).alias("b")
... )
>>> str(result.collect_column("b")[0].as_py())
'2021-07-15 12:30:00'
>>> str(result.collect_column("b")[1].as_py())
'2021-01-01 00:00:00'
"""
return Expr(f.date_bin(stride.expr, source.expr, origin.expr))


def make_date(year: Expr, month: Expr, day: Expr) -> Expr:
"""Make a date from year, month and day component parts."""
"""Make a date from year, month and day component parts.

Examples:
>>> from datetime import date
>>> ctx = dfn.SessionContext()
>>> df = ctx.from_pydict({"y": [2024], "m": [1], "d": [15]})
>>> result = df.select(
... dfn.functions.make_date(dfn.col("y"), dfn.col("m"),
... dfn.col("d")).alias("dt"))
>>> result.collect_column("dt")[0].as_py()
datetime.date(2024, 1, 15)
"""
return Expr(f.make_date(year.expr, month.expr, day.expr))


Expand Down Expand Up @@ -1839,7 +1989,19 @@ def named_struct(name_pairs: list[tuple[str, Expr]]) -> Expr:


def from_unixtime(arg: Expr) -> Expr:
"""Converts an integer to RFC3339 timestamp format string."""
"""Converts an integer to RFC3339 timestamp format string.

Examples:
>>> ctx = dfn.SessionContext()
>>> df = ctx.from_pydict({"a": [0]})
>>> result = df.select(
... dfn.functions.from_unixtime(
... dfn.col("a")
... ).alias("ts")
... )
>>> str(result.collect_column("ts")[0].as_py())
'1970-01-01 00:00:00'
"""
return Expr(f.from_unixtime(arg.expr))

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@kosiew kosiew Mar 13, 2026

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The PR title is Add docstring examples for scalar temporal functions, but to_date, to_time, and to_local_time still have no examples. Since those are public temporal wrappers in the same section, this feels incomplete.


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