45 lines
1.2 KiB
Python
45 lines
1.2 KiB
Python
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import re
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_match_duration = re.compile(r"^(-?\d+\.?\d*)(s|ms)$").match
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class DurationError(Exception):
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"""
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Exception indicating a general issue with a CSS duration.
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"""
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class DurationParseError(DurationError):
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"""
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Indicates a malformed duration string that could not be parsed.
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"""
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def _duration_as_seconds(duration: str) -> float:
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"""
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Args:
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duration: A string of the form `"2s"` or `"300ms"`, representing 2 seconds and
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300 milliseconds respectively. If no unit is supplied, e.g. `"2"`, then the duration is
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assumed to be in seconds.
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Raises:
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DurationParseError: If the argument `duration` is not a valid duration string.
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Returns:
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The duration in seconds.
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"""
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match = _match_duration(duration)
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if match:
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value, unit_name = match.groups()
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value = float(value)
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if unit_name == "ms":
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duration_secs = value / 1000
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else:
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duration_secs = value
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else:
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try:
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duration_secs = float(duration)
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except ValueError:
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raise DurationParseError(f"{duration!r} is not a valid duration.") from None
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return duration_secs
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