FilesExpand file tree

 master

/

null.py

Copy path

Blame

More file actions

Blame

More file actions

Latest commit

 

History

History

History

81 lines (57 loc) · 1.54 KB

 master

/

null.py

Copy path

Top

File metadata and controls

• Code
• Blame

81 lines (57 loc) · 1.54 KB

Raw

Copy raw file

Download raw file

Open symbols panel

Edit and raw actions

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

50

51

52

53

54

55

56

57

58

59

60

61

62

63

64

65

66

67

68

69

70

71

72

73

74

75

76

77

78

79

80

81

#!/user/bin/env python

"""http://code.activestate.com/recipes/68205-null-object-design-pattern/"""

class Null:

def __init__(self, *args, **kwargs):

"""Ignore parameters."""

return None

def __call__(self, *args, **kwargs):

"""Ignore method calls."""

return self

def __getattr__(self, mname):

"""Ignore attribute requests."""

return self

def __setattr__(self, name, value):

"""Ignore attribute setting."""

return self

def __delattr__(self, name):

"""Ignore deleting attributes."""

return self

def __repr__(self):

"""Return a string representation."""

return "<Null>"

def __str__(self):

"""Convert to a string and return it."""

return "Null"

def test():

"""Perform some decent tests, or rather: demos."""

# constructing and calling

n = Null()

print(n)

n = Null('value')

print(n)

n = Null('value', param='value')

print(n)

n()

n('value')

n('value', param='value')

print(n)

# attribute handling

n.attr1

print('attr1', n.attr1)

n.attr1.attr2

n.method1()

n.method1().method2()

n.method('value')

n.method(param='value')

n.method('value', param='value')

n.attr1.method1()

n.method1().attr1

n.attr1 = 'value'

n.attr1.attr2 = 'value'

del n.attr1

del n.attr1.attr2.attr3

# representation and conversion to a string

assert repr(n) == '<Null>'

assert str(n) == 'Null'

if __name__ == '__main__':

test()