This proposal is about adding a builtin function or a package to the standard
library to access an element in an object hierarchy with default behavior i.e.
if at any level the attribute/key/index does not exist in the path the function
returns a default value.
Motivation: mapping an object tree to a tuple or a flat object cannot be
achieved compactly with proper error handling.
Need: I have found a half dozen of packages implementing this functionality on
github and there is a high number of loosely related libraries.
Here is a motivating example:
animal = {
'name': 'Wombat',
'avg_properties': {
'height': {'value': 66, 'unit': 'cm'},
'length':{'value': 108, 'unit': 'cm'},
'weight': {'value': 27, 'unit': 'kg'}
}
}
assert getpath(animal, ('avg_properties', 'length', 'value'), default='-') ==
108
assert getpath(animal, ('min_properties', 'length', 'value'), default='-') ==
'-'
assert getpaths(animal, 'avg_properties.length.value', default='-') == 108
assert getpaths(animal, 'avg_properties/width/value', sep='/') == None
I created a package to demonstrate the idea:
https://github.com/axonmatics/quickpath
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