import random
from datetime import datetime, timedelta
from typing import List
from langchain_core.exceptions import OutputParserException
from langchain_core.output_parsers import BaseOutputParser
from langchain_core.utils import comma_list
def _generate_random_datetime_strings(
pattern: str,
n: int = 3,
start_date: datetime = datetime(1, 1, 1),
end_date: datetime = datetime.now() + timedelta(days=3650),
) -> List[str]:
"""Generates n random datetime strings conforming to the
given pattern within the specified date range.
Pattern should be a string containing the desired format codes.
start_date and end_date should be datetime objects representing
the start and end of the date range.
"""
examples = []
delta = end_date - start_date
for i in range(n):
random_delta = random.uniform(0, delta.total_seconds())
dt = start_date + timedelta(seconds=random_delta)
date_string = dt.strftime(pattern)
examples.append(date_string)
return examples
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 used as the datetime format."""
def get_format_instructions(self) -> str:
examples = comma_list(_generate_random_datetime_strings(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!"
)
def parse(self, response: str) -> datetime:
try:
return datetime.strptime(response.strip(), self.format)
except ValueError as e:
raise OutputParserException(
f"Could not parse datetime string: {response}"
) from e
@property
def _type(self) -> str:
return "datetime"