Coverage for /usr/lib/python3/dist-packages/sympy/core/rules.py: 57%

1""" 

2Replacement rules. 

3""" 

4 

5class Transform: 

6 """ 

7 Immutable mapping that can be used as a generic transformation rule. 

8 

9 Parameters 

10 ========== 

11 

12 transform : callable 

13 Computes the value corresponding to any key. 

14 

15 filter : callable, optional 

16 If supplied, specifies which objects are in the mapping. 

17 

18 Examples 

19 ======== 

20 

21 >>> from sympy.core.rules import Transform 

22 >>> from sympy.abc import x 

23 

24 This Transform will return, as a value, one more than the key: 

25 

26 >>> add1 = Transform(lambda x: x + 1) 

27 >>> add1[1] 

28 2 

29 >>> add1[x] 

30 x + 1 

31 

32 By default, all values are considered to be in the dictionary. If a filter 

33 is supplied, only the objects for which it returns True are considered as 

34 being in the dictionary: 

35 

36 >>> add1_odd = Transform(lambda x: x + 1, lambda x: x%2 == 1) 

37 >>> 2 in add1_odd 

38 False 

39 >>> add1_odd.get(2, 0) 

40 0 

41 >>> 3 in add1_odd 

42 True 

43 >>> add1_odd[3] 

44 4 

45 >>> add1_odd.get(3, 0) 

46 4 

47 """ 

48 

49 def __init__(self, transform, filter=lambda x: True): 

50 self._transform = transform 

51 self._filter = filter 

52 

53 def __contains__(self, item): 

54 return self._filter(item) 

55 

56 def __getitem__(self, key): 

57 if self._filter(key): 

58 return self._transform(key) 

59 else: 

60 raise KeyError(key) 

61 

62 def get(self, item, default=None): 

63 if item in self: 

64 return self[item] 

65 else: 

66 return default