Coverage for /pythoncovmergedfiles/medio/medio/usr/local/lib/python3.8/site-packages/IPython/utils/contexts.py: 29%

1# encoding: utf-8 

2"""Miscellaneous context managers. 

3""" 

4 

5import warnings 

6 

7# Copyright (c) IPython Development Team. 

8# Distributed under the terms of the Modified BSD License. 

9 

10 

11class preserve_keys(object): 

12 """Preserve a set of keys in a dictionary. 

13 

14 Upon entering the context manager the current values of the keys 

15 will be saved. Upon exiting, the dictionary will be updated to 

16 restore the original value of the preserved keys. Preserved keys 

17 which did not exist when entering the context manager will be 

18 deleted. 

19 

20 Examples 

21 -------- 

22 

23 >>> d = {'a': 1, 'b': 2, 'c': 3} 

24 >>> with preserve_keys(d, 'b', 'c', 'd'): 

25 ... del d['a'] 

26 ... del d['b'] # will be reset to 2 

27 ... d['c'] = None # will be reset to 3 

28 ... d['d'] = 4 # will be deleted 

29 ... d['e'] = 5 

30 ... print(sorted(d.items())) 

31 ... 

32 [('c', None), ('d', 4), ('e', 5)] 

33 >>> print(sorted(d.items())) 

34 [('b', 2), ('c', 3), ('e', 5)] 

35 """ 

36 

37 def __init__(self, dictionary, *keys): 

38 self.dictionary = dictionary 

39 self.keys = keys 

40 

41 def __enter__(self): 

42 # Actions to perform upon exiting. 

43 to_delete = [] 

44 to_update = {} 

45 

46 d = self.dictionary 

47 for k in self.keys: 

48 if k in d: 

49 to_update[k] = d[k] 

50 else: 

51 to_delete.append(k) 

52 

53 self.to_delete = to_delete 

54 self.to_update = to_update 

55 

56 def __exit__(self, *exc_info): 

57 d = self.dictionary 

58 

59 for k in self.to_delete: 

60 d.pop(k, None) 

61 d.update(self.to_update)