GetNested¶
Access a nested field or item of a specified object, which is identified by a path, analogous to a file path (or a chain of ".f
ield[10]['key'].something.else" syntax in some programming languages). The path is specified using a syntax that can be selected using the 'syntax' parameter. If the field is not found, return the value specified by the 'notfound' port or raise an error (notfound is respected regardless of whether the object has a fixed set of fields or an open-ended set). However, if the key is of the wrong data type (e.g. indexing an array with a string) or is syntactically malformed, an error will be raised even if notfound is not set to '(error)'. The available fields depend on the object being accessed, and can be looked up in the documentation. Typically, the error message will also indicate the available fields. If either the field or the data are none, the output will be None. Using this node requires some knowledge of the structure of the incoming data Packet. Objects use a : prefix (:block). For example, to extract a list of names from a feature axis for a stream (Chunk object) called "eeg", one would set the "path" property to: :chunks|eeg|:block|:axes|:feature|:names. This will return a list. To extract the last item along the Feature axis (a string), the syntax would be: :chunks|eeg|:block|:axes|:feature|:names|-1. To extract the list of event markers from a stream named markers, the syntax would be: :chunks|markers|:block|:axes|:instance|:data|Marker. You can view the structure of your packet using InspectPacket or Print nodes. The Packet class has some special methods you can use in the path, the most useful perhaps is :first(), which returns the first stream (chunk) in the packet. It also accepts additional criteria, i.e., :first(nonempty=True) will return the first nonempty stream. The full list of arguments that can be passed to first() is the same as the enumerate_chunks() Python function (see the documentation for the packet submodule in the developer documentation). Example: :first()|:block|:axes|:instance|:data|Marker.
Version 1.2.0
Ports/Properties¶
data¶
Data to process.
path¶
Path to field/item. See syntax option for details.
syntax¶
Syntax of the path. The pipe syntax looks as in " :field | 10 | 'quoted string key' | unquoted string key | 15 | :other_field | 5" where item may be a single-, double-, or unquoted string, a number, or one of the special symbols True/False/None. In practice, quoted strings are only rarely needed, namely to write strings that would otherwise parse as a different type (number, True/False/None, :field) or lose any intended leading/trailing whitespace. However, for procedurally generated (string-concatenated) paths, strings should always be quoted. The lax syntax is a more permissive version of the pipe syntax, where the : is optional; this can be ambiguous in the rare case that an object both has a field named :field and an item named field. The python syntax is the index syntax known from Python, which looks as in .field[10]['quoted string key']['unquoted string key'][15]. However, note that, at present, method calls like .first() are not permitted in python mode.
notfound¶
Value to return if the field is not found. If set to raise, an error will be raised. Ignore will proceed regardless (a None value will be output). You can also enter a custom value here that will be returned if the field is not found. (Note: The value (error) will also raise an error for backward compatibility.)
set_breakpoint¶
Set a breakpoint on this node. If this is enabled, your debugger (if one is attached) will trigger a breakpoint.
metadata¶
User-definable meta-data associated with the node. Usually reserved for technical purposes.