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JsonWriter

from tdw.add_ons.json_writer import JsonWriter

Dump JSON data of objects per-frame. Objects in this case refers not to TDW objects but to Python objects, such as a Robot add-on or an arbitrary dictionary of data.

Per frame, these objects will be read, encoded into Python dictionaries, and written out as serialized JSON data files.

The JSON files can be read and reloaded like any other file with JSON information. However, TDW does not provide a means of automatically converting serialized JSON data back into objects.

Data is converted to JSON-serializable format as follows:

  • Numpy arrays are converted to Python lists.
  • Numpy RandomState objects, which many TDW classes use, are not serialized and receive a null value.
  • bytes and bytearray objects are converted into base64 strings.
  • Path objects are converted into absolute filepath strings.
  • Some classes, namely those in the tdw.FBOutput namespace, can't readily be serialized to a dictionary; their values are instead set to null.
  • Enum values are converted to their string representation i.e. value.name.
  • Dictionaries that have non-string keys have all of their keys converted into strings i.e. str(key).

Fields

  • objects A dictionary of objects to serialize. Key = A name or identifier for the object, for example "robot". Value = A data object, for example a Robot.

  • output_directory The root output directory as a Path. If this doesn't exist, it will be created.

  • commands These commands will be appended to the commands of the next communicate() call.

  • initialized If True, this module has been initialized.

Functions

__init__

JsonJsonWriter(objects, output_directory)

JsonJsonWriter(objects, output_directory, indent=2, include_hidden_fields=False, zero_padding=8)

Parameter Type Default Description
objects Dict[str, object] A dictionary of objects to serialize. Key = A name or identifier for the object, for example "robot". Value = A data object, for example a Robot.
output_directory PATH The root output directory as a string or Path. If this doesn't exist, it will be created.
indent int 2 The indentation level of the output JSON strings.
include_hidden_fields bool False If True, include hidden fields in the JSON data i.e. any fields which have names that begin with _. This will give you all of the data, but often you won't want this. Many TDW classes hold megabytes of data in hidden fields, which is trivial to do in memory but serializing this data can be very slow.
zero_padding int 8 How many zeros to append to the file name. By default, the name of the file of the first frame will be 00000000.txt.

reset

self.reset()

This will reset the frame count.

read

self.read(path)

Read saved ouput data.

Parameter Type Default Description
path Union[str, Path, int] The path to the frame file. This can be a string or Path file path or an integer. If this is an integer, it represents the frame number; the file is assumed to be in self.output_directory.

Returns: If path is a string or a Path, this will return a dictionary. If path is an integer, this will return a dictionary of dictionaries where the key is the object name (e.g. "robot") and the value is the corresponding dictionary.

get_initialization_commands

self.get_initialization_commands()

This function gets called exactly once per add-on. To re-initialize, set self.initialized = False.

Returns: A list of commands that will initialize this add-on.

on_send

self.on_send(resp)

This is called within Controller.communicate(commands) after commands are sent to the build and a response is received.

Use this function to send commands to the build on the next Controller.communicate(commands) call, given the resp response. Any commands in the self.commands list will be sent on the next Controller.communicate(commands) call.

Parameter Type Default Description
resp List[bytes] The response from the build.

before_send

self.before_send(commands)

This is called within Controller.communicate(commands) before sending commands to the build. By default, this function doesn't do anything.

Parameter Type Default Description
commands List[dict] The commands that are about to be sent to the build.

get_early_initialization_commands

self.get_early_initialization_commands()

This function gets called exactly once per add-on. To re-initialize, set self.initialized = False.

These commands are added to the list being sent on communicate() before any other commands, including those added by the user and by other add-ons.

Usually, you shouldn't override this function. It is useful for a small number of add-ons, such as loading screens, which should initialize before anything else.

Returns: A list of commands that will initialize this add-on.