Coverage for python/lsst/images/serialization/_external_metadata.py: 26%

1# This file is part of lsst-images. 

2# 

3# Developed for the LSST Data Management System. 

4# This product includes software developed by the LSST Project 

5# (https://www.lsst.org). 

6# See the COPYRIGHT file at the top-level directory of this distribution 

7# for details of code ownership. 

8# 

9# Use of this source code is governed by a 3-clause BSD-style 

10# license that can be found in the LICENSE file. 

11 

12from __future__ import annotations 

13 

14__all__ = ("EmptyExternalMetadata", "ExternalMetadata", "ExternalMetadataValue") 

15 

16from abc import abstractmethod 

17from collections.abc import Iterator, Mapping 

18 

19type ExternalMetadataValue = bool | int | float | complex | str | None 

20 

21 

22class ExternalMetadata(Mapping[str, ExternalMetadataValue]): 

23 """Read-only access to metadata that was carried in from an external 

24 source, such as the primary header of a FITS file, and is not part of 

25 the data model. 

26 

27 Notes 

28 ----- 

29 Lookups and membership tests are case-insensitive. Iteration yields 

30 each key once, in the form the underlying source reports it. When a key 

31 is repeated in the source, which of its values ``[]`` returns is 

32 unspecified; use `get_all` to obtain every value. 

33 """ 

34 

35 @abstractmethod 

36 def get_all(self, key: str) -> tuple[ExternalMetadataValue, ...]: 

37 """Return every value for a key, in source order. 

38 

39 Parameters 

40 ---------- 

41 key 

42 Key to look up (case-insensitive). 

43 

44 Returns 

45 ------- 

46 values : `tuple` 

47 All values for ``key``. 

48 

49 Raises 

50 ------ 

51 KeyError 

52 Raised if ``key`` is not present. 

53 """ 

54 raise NotImplementedError() 

55 

56 def __repr__(self) -> str: 

57 return f"{type(self).__name__}({dict(self)!r})" 

58 

59 

60class EmptyExternalMetadata(ExternalMetadata): 

61 """An `ExternalMetadata` with no keys.""" 

62 

63 def __getitem__(self, key: str) -> ExternalMetadataValue: 

64 raise KeyError(key) 

65 

66 def __iter__(self) -> Iterator[str]: 

67 return iter(()) 

68 

69 def __len__(self) -> int: 

70 return 0 

71 

72 def get_all(self, key: str) -> tuple[ExternalMetadataValue, ...]: 

73 # Docstring inherited. 

74 raise KeyError(key)