Skip to content

Add docstring examples for Scalar temporal functions #1424

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
ntjohnson1 wants to merge 1 commit into
base: main
Choose a base branch
from
Open

Add docstring examples for Scalar temporal functions #1424

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
220 changes: 212 additions & 8 deletions python/datafusion/functions.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1162,6 +1162,20 @@ 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 @@ -1222,6 +1236,18 @@ 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 @@ -1230,6 +1256,18 @@ 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 @@ -1238,6 +1276,18 @@ 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 @@ -1246,6 +1296,18 @@ 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 @@ -1254,69 +1316,198 @@ 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())


def datepart(part: Expr, date: Expr) -> Expr:
"""Return a specified part of a date.

This is an alias for :py:func:`date_part`.

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.datepart(dfn.lit("month"), dfn.col("a")).alias("m"))
>>> result.collect_column("m")[0].as_py()
7
"""
return date_part(part, date)


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))


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

This is an alias for :py:func:`date_part`.

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.extract(dfn.lit("day"), dfn.col("a")).alias("d"))
>>> result.collect_column("d")[0].as_py()
15
"""
return date_part(part, date)


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))


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

This is an alias for :py:func:`date_trunc`.

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.datetrunc(
... dfn.lit("year"), dfn.col("a")
... ).alias("t")
... )
>>> str(result.collect_column("t")[0].as_py())
'2021-01-01 00:00:00'
"""
return date_trunc(part, date)


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()
>>> result = ctx.sql(
... "SELECT date_bin(interval '1 day',"
... " timestamp '2021-07-15 12:34:56',"
... " timestamp '2021-01-01') as b"
... )
>>> str(result.collect_column("b")[0].as_py())
'2021-07-15 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 @@ -1393,7 +1584,20 @@ 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))


Expand Down
Loading