Source code for langchain.output_parsers.datetime
from datetime import datetime, timedelta, timezone
from langchain_core.exceptions import OutputParserException
from langchain_core.output_parsers import BaseOutputParser
from langchain_core.utils import comma_list
[docs]
class DatetimeOutputParser(BaseOutputParser[datetime]):
"""Parse the output of an LLM call to a datetime."""
format: str = "%Y-%m-%dT%H:%M:%S.%fZ"
"""The string value that is used as the datetime format.
Update this to match the desired datetime format for your application.
"""
[docs]
def get_format_instructions(self) -> str:
"""Returns the format instructions for the given format."""
if self.format == "%Y-%m-%dT%H:%M:%S.%fZ":
examples = comma_list(
[
"2023-07-04T14:30:00.000000Z",
"1999-12-31T23:59:59.999999Z",
"2025-01-01T00:00:00.000000Z",
],
)
else:
try:
now = datetime.now(tz=timezone.utc)
examples = comma_list(
[
now.strftime(self.format),
(now.replace(year=now.year - 1)).strftime(self.format),
(now - timedelta(days=1)).strftime(self.format),
],
)
except ValueError:
# Fallback if the format is very unusual
examples = f"e.g., a valid string in the format {self.format}"
return (
f"Write a datetime string that matches the "
f"following pattern: '{self.format}'.\n\n"
f"Examples: {examples}\n\n"
f"Return ONLY this string, no other words!"
)
[docs]
def parse(self, response: str) -> datetime:
"""Parse a string into a datetime object."""
try:
return datetime.strptime(response.strip(), self.format) # noqa: DTZ007
except ValueError as e:
msg = f"Could not parse datetime string: {response}"
raise OutputParserException(msg) from e
@property
def _type(self) -> str:
return "datetime"