iframe-proxy | Sunbelt Computer Software

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#!/usr/bin/env python
# -*- coding: utf-8 -*-
"""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('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__':
### OUTPUT ###
# attr1 Null

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