mirror of
https://github.com/vale981/ray
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32 lines
883 B
Python
32 lines
883 B
Python
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import logging
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import os
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from typing import Iterator, Optional
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logger = logging.getLogger(__name__)
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def file_tail_iterator(path: str) -> Iterator[Optional[str]]:
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"""Yield lines from a file as it's written.
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Returns lines in batches opportunistically.
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Returns None until the file exists or if no new line has been written.
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"""
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if not isinstance(path, str):
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raise TypeError(f"path must be a string, got {type(path)}.")
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while not os.path.exists(path):
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logger.debug(f"Path {path} doesn't exist yet.")
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yield None
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with open(path, "r") as f:
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lines = ""
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while True:
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curr_line = f.readline()
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# readline() returns empty string when there's no new line.
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if curr_line:
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lines += curr_line
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else:
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yield lines or None
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lines = ""
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