Right, if you simply pass in a string it is not a BuiltInParameter. Here’s a rewritten example:
import clr
clr.AddReference('RevitAPI')
from Autodesk.Revit.DB import BuiltInParameter
from System import Enum
key = 'ALL_MODEL_TYPE_COMMENTS'
names = Enum.GetNames(BuiltInParameter)
values = Enum.GetValues(BuiltInParameter)
bip_dict = dict(zip(names, values))
# Returns a BuiltInParameter given its name (key)
bip = bip_dict[key]
# Assume wall is a valid Element
param = wall.Parameter[bip]
param_value = param.AsString()
In your above example, BaseMatch_Parameter_Key is not a member of the BuiltInParameter Enum. Members are accessed by their name, such as BuiltInParameter.ALL_MODEL_TYPE_COMMENTS, but this is not a string. If that were the case, it would be written as BuiltInParameter.“ALL_MODEL_TYPE_COMMENTS”. So, it isn’t possible to replace one of the member names with a string in that manner. The process I have illustrated above creates a dictionary where the keys are the member names and the values are the corresponding BuiltInParameter values.
{
'PATH_OF_TRAVEL_FROM_ROOM': BuiltInParameter.PATH_OF_TRAVEL_FROM_ROOM,
'PATH_OF_TRAVEL_TO_ROOM': BuiltInParameter.PATH_OF_TRAVEL_TO_ROOM,
'STEEL_ELEM_PROFILE_VOLUME': BuiltInParameter.STEEL_ELEM_PROFILE_VOLUME
etc...
}