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import random |
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from datetime import datetime, timedelta |
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from typing import List |
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from langchain_core.exceptions import OutputParserException |
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from langchain_core.output_parsers import BaseOutputParser |
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from langchain_core.utils import comma_list |
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def _generate_random_datetime_strings( |
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pattern: str, |
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n: int = 3, |
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start_date: datetime = datetime(1, 1, 1), |
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end_date: datetime = datetime.now() + timedelta(days=3650), |
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) -> List[str]: |
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"""Generates n random datetime strings conforming to the |
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given pattern within the specified date range. |
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Pattern should be a string containing the desired format codes. |
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start_date and end_date should be datetime objects representing |
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the start and end of the date range. |
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""" |
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examples = [] |
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delta = end_date - start_date |
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for i in range(n): |
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random_delta = random.uniform(0, delta.total_seconds()) |
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dt = start_date + timedelta(seconds=random_delta) |
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date_string = dt.strftime(pattern) |
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examples.append(date_string) |
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return examples |
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class DatetimeOutputParser(BaseOutputParser[datetime]): |
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"""Parse the output of an LLM call to a datetime.""" |
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format: str = "%Y-%m-%dT%H:%M:%S.%fZ" |
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"""The string value that used as the datetime format.""" |
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def get_format_instructions(self) -> str: |
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examples = comma_list(_generate_random_datetime_strings(self.format)) |
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return ( |
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f"Write a datetime string that matches the " |
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f"following pattern: '{self.format}'.\n\n" |
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f"Examples: {examples}\n\n" |
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f"Return ONLY this string, no other words!" |
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) |
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def parse(self, response: str) -> datetime: |
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try: |
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return datetime.strptime(response.strip(), self.format) |
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except ValueError as e: |
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raise OutputParserException( |
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f"Could not parse datetime string: {response}" |
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) from e |
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@property |
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def _type(self) -> str: |
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return "datetime" |
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