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Last active August 29, 2015 13:56
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Replaces nested attributes on namedtuples
def attr_update(obj, child=None, _call=True, **kwargs):
'''Updates attributes on nested namedtuples.
Accepts a namedtuple object, a string denoting the nested namedtuple to update,
and keyword parameters for the new values to assign to its attributes.
You may set _call=False if you wish to assign a callable to a target attribute.
Example: to replace obj.x.y.z, do attr_update(obj, "x.y", z=new_value).
Example: attr_update(obj, "x.y.z", prop1=lambda prop1: prop1*2, prop2='new prop2')
Example: attr_update(obj, "x.y", lambda z: z._replace(prop1=prop1*2, prop2='new prop2'))
Example: attr_update(obj, alpha=lambda alpha: alpha*2, beta='new beta')
def call_val(old, new):
if _call and callable(new):
new_value = new(old)
new_value = new
return new_value
def replace_(to_replace, parts):
parent = reduce(getattr, parts, obj)
new_values = {k: call_val(getattr(parent, k), v) for k,v in to_replace.iteritems()}
new_parent = parent._replace(**new_values)
if len(parts) == 0:
return new_parent
return {parts[-1]: new_parent}
if child in (None, ""):
parts = tuple()
parts = child.split(".")
return reduce(
(parts[:i] for i in xrange(len(parts), -1, -1)),
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