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To avoid NoneType AttributeError exception on chained attributes

Project description

When you access an object with chained attributes

info = obj.a.b.c.d or 'Unknown'

Usually, it will failed when one intermediate attribute return ‘None‘

if obj.a returns None
obj.a.b.c.d will fail with that exception :
AttributeError: 'NoneType' object has no attribute 'b'

To avoid that, instead of returning a ‘None‘ value, one should return ‘NoAttr‘, by this way, even next chained attribute will return ‘NoAttr‘

if obj.a returns NoAttr
obj.a.b.c.d will not fail and will return NoAttr

‘NoAttr‘ can be seen as False, 0, ‘’, [] or {} depending on the context, so

if obj.a returns NoAttr

obj.a.b.c.d or 'Unknown' will return 'Unknown'

for i in obj.a.b.c.d:
    print i
prints nothing

obj.a.b.c.d + 1 returns 1

obj.a.b.c.d.anyfunc() returns NoAttr

but for ljust(), rjust(), rfind(), find(), rindex(), index(), count()
NoAttr is seen as '' :

obj.a.b.c.d.ljust(3) returns '   '


0.0.6 (2016-03-11)

remove __or__ and __rshift__ definition for python_textops

0.0.5 (2015-10-13)

add as_list property

0.0.4 (2015-08-19)

add __setattr__ to avoid any modification

0.0.3 (2015-07-27)

First official version

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