Coverage for src/CSET/operators/_utils.py: 100%

1# Copyright 2022-2024 Met Office and contributors. 

2# 

3# Licensed under the Apache License, Version 2.0 (the "License"); 

4# you may not use this file except in compliance with the License. 

5# You may obtain a copy of the License at 

6# 

7# http://www.apache.org/licenses/LICENSE-2.0 

8# 

9# Unless required by applicable law or agreed to in writing, software 

10# distributed under the License is distributed on an "AS IS" BASIS, 

11# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 

12# See the License for the specific language governing permissions and 

13# limitations under the License. 

14 

15""" 

16Common operator functionality used across CSET. 

17 

18Functions below should only be added if it is not suitable as a standalone 

19operator, and will be used across multiple operators. 

20""" 

21 

22import iris 

23import iris.cube 

24 

25 

26def get_cube_yxcoordname(cube: iris.cube.Cube) -> tuple[str, str]: 

27 """ 

28 Return horizontal coordinate name(s) from a given cube. 

29 

30 Arguments 

31 --------- 

32 

33 cube: iris.cube.Cube 

34 An iris cube which will be checked to see if it contains coordinate 

35 names that match a pre-defined list of acceptable horizontal 

36 coordinate names. 

37 

38 Returns 

39 ------- 

40 (y_coord, x_coord) 

41 A tuple containing the horizontal coordinate name for latitude and longitude respectively 

42 found within the cube. 

43 

44 Raises 

45 ------ 

46 ValueError 

47 If a unique y/x horizontal coordinate cannot be found. 

48 """ 

49 # Acceptable horizontal coordinate names. 

50 X_COORD_NAMES = ["longitude", "grid_longitude", "projection_x_coordinate", "x"] 

51 Y_COORD_NAMES = ["latitude", "grid_latitude", "projection_y_coordinate", "y"] 

52 

53 # Get a list of coordinate names for the cube 

54 coord_names = [coord.name() for coord in cube.coords()] 

55 

56 # Check which x-coordinate we have, if any 

57 x_coords = [coord for coord in coord_names if coord in X_COORD_NAMES] 

58 if len(x_coords) != 1: 

59 raise ValueError("Could not identify a unique x-coordinate in cube") 

60 

61 # Check which y-coordinate we have, if any 

62 y_coords = [coord for coord in coord_names if coord in Y_COORD_NAMES] 

63 if len(y_coords) != 1: 

64 raise ValueError("Could not identify a unique y-coordinate in cube") 

65 

66 return (y_coords[0], x_coords[0])