commaai/openpilot · error · URLFileException

Invalid whence value

Error message

Invalid whence value

What it means

URLFile.seek only handles the three standard whence values: os.SEEK_SET (0), SEEK_CUR (1), SEEK_END (2). Anything else — e.g. passing a string, a typo'd constant, or a non-standard whence — raises. Note pos is int()-coerced, but whence is compared literally.

Source

Thrown at openpilot/tools/lib/url_file.py:209

    if len(parts) != len(ranges):
      raise URLFileException(f"Expected {len(ranges)} parts, got {len(parts)} ({self._url})")
    return parts

  def seekable(self) -> bool:
    return True

  def seek(self, pos: int, whence: int = 0) -> int:
    pos = int(pos)
    if whence == os.SEEK_SET:
      self._pos = pos
    elif whence == os.SEEK_CUR:
      self._pos += pos
    elif whence == os.SEEK_END:
      length = self.get_length()
      assert length != -1, "Cannot seek from end on unknown length file"
      self._pos = length + pos
    else:
      raise URLFileException("Invalid whence value")
    return self._pos

  def tell(self) -> int:
    return self._pos

  @property
  def name(self) -> str:
    return self._url


os.register_at_fork(after_in_child=URLFile.reset)

View on GitHub (pinned to 516ec1e682)

Solutions

1. Use os.SEEK_SET / os.SEEK_CUR / os.SEEK_END (or 0/1/2) only
2. Validate/normalize whence before calling seek when it comes from external input
3. For seek-from-end, ensure the file length is known (HEAD succeeded) or the adjacent assert will fire

Example fix

# before
uf.seek(10, whence)

# after
import os
assert whence in (os.SEEK_SET, os.SEEK_CUR, os.SEEK_END)
uf.seek(10, whence)

import os
assert whence in (os.SEEK_SET, os.SEEK_CUR, os.SEEK_END)

def is_valid_whence(w) -> bool:
    import os
    return w in (os.SEEK_SET, os.SEEK_CUR, os.SEEK_END)

When it happens

Trigger: Calling uf.seek(n, 3), uf.seek(n, 'start'), or passing whence from an unvalidated variable. Also seek(..., SEEK_END) with unknown length hits the adjacent assert instead.

Common situations: Code adapted from io implementations that accept extra whence values; passing numpy ints or enum values that don't equal 0/1/2; user-supplied seek parameters.

Related errors

• Profile nickname must be 64 bytes or less
• Confirmation code required but not provided
• Invalid activation code format
• not a valid request or response
• -32000

AI-assisted analysis of commaai/openpilot@516ec1e682 (2026-08-15). Data as JSON: /api/errors/697261f82e0c2adc. Report an issue: GitHub.