1'''
2Custom exceptions raised by pytz.
3'''
4
5__all__ = [
6    'UnknownTimeZoneError', 'InvalidTimeError', 'AmbiguousTimeError',
7    'NonExistentTimeError',
8]
9
10
11class Error(Exception):
12    '''Base class for all exceptions raised by the pytz library'''
13
14
15class UnknownTimeZoneError(KeyError, Error):
16    '''Exception raised when pytz is passed an unknown timezone.
17
18    >>> isinstance(UnknownTimeZoneError(), LookupError)
19    True
20
21    This class is actually a subclass of KeyError to provide backwards
22    compatibility with code relying on the undocumented behavior of earlier
23    pytz releases.
24
25    >>> isinstance(UnknownTimeZoneError(), KeyError)
26    True
27
28    And also a subclass of pytz.exceptions.Error, as are other pytz
29    exceptions.
30
31    >>> isinstance(UnknownTimeZoneError(), Error)
32    True
33
34    '''
35    pass
36
37
38class InvalidTimeError(Error):
39    '''Base class for invalid time exceptions.'''
40
41
42class AmbiguousTimeError(InvalidTimeError):
43    '''Exception raised when attempting to create an ambiguous wallclock time.
44
45    At the end of a DST transition period, a particular wallclock time will
46    occur twice (once before the clocks are set back, once after). Both
47    possibilities may be correct, unless further information is supplied.
48
49    See DstTzInfo.normalize() for more info
50    '''
51
52
53class NonExistentTimeError(InvalidTimeError):
54    '''Exception raised when attempting to create a wallclock time that
55    cannot exist.
56
57    At the start of a DST transition period, the wallclock time jumps forward.
58    The instants jumped over never occur.
59    '''
60