======
NoAttr
======
When accessing an object with chained attributes, ::
info = obj.a.b.c.d or 'Unknown'
naïvely this will fail as soon as one of the intermediate attributes returns ``None``: ::
>>> obj.a
None
>>> obj.a.b.c.
AttributeError: 'NoneType' object has no attribute 'b'
*NoAttr* gives you a way around this in cases where a series of ``None`` checks would be too much effort and result in complex code.
Instead of returning ``None``, you want to return an instance of ``NoAttr``, which will caused hierarchical attribute accesses to keep returning ``NoAttr`` until the end of the chain ::
>>> from noattr import NoAttr
>>> obj = NoAttr
>>> obj.a
NoAttr
>>> obj.a.b.c.d
NoAttr
*NoAttr* behaves as a "falsy" value, meaning that it can stand for ``None``, ``False``, ``0``, ``''``, ``[]`` or ``{}``, depending on context. Here are some examples: ::
>>> obj.a
NoAttr
>>> obj.a.b.c.d or 'Unknown' # behaves like a falsy value
'Unknown'
>>> for i in obj.a.b.c.d: # behaves like an enumerable that does not yield a value
... print(i)
(no output)
>>> len(obj.a.b.c.d) # behaves like an empty collection
0
>>> obj.a.b.c.d + 1 # behaves like a 0
1
>>> obj.a.b.c.d.anyfunc() # behaves like a callable
NoAttr
However, for ``ljust()``, ``rjust()``, ``rfind()``, ``find()``, ``rindex()``, ``index()``, and ``count()``, *NoAttr* is seen as a single whitespace character (``' '``) to preserve the expected behavior of these methods: ::
>>> obj.a.b.c.d.ljust(3)
' '
Installation
############
$ ``pip install noattr``
News
====
0.0.8 (2018-08-24)
------------------
__iter__() now returns an empty iter
0.0.7 (2018-08-21)
------------------
Update code for python3 compatibility
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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