Migrating to 3.0

If you have a working program using NXT-Python 2, you will have to make changes to port it to NXT-Python 3.

Porting to Python 3

First of all you need to port your code to Python 3, there is an guide in Python documentation. You do not need to worry about keeping the code compatible with Python 2 as it is no longer supported.

There is also an automatic script to ease the porting, called 2to3.

One major change in Python is the distinction between text string (str) and binary string (bytes). This means that you need to make sure to use the right one when passing arguments to NXT-Python functions.

Porting to NXT-Python 3

Next step is to adapt the code for NXT-Python.

Major Changes

The nxt.locator.find_one_brick() function has been removed and replaced with the simpler nxt.locator.find() function. Actually, the whole nxt.locator has been replaced.

Many debug arguments have been removed, now NXT-Python uses the logging module to log messages. If you want to enable debug messages, use this code before calling any NXT-Python function:

import logging
logging.basicConfig(level=logging.DEBUG)

The nxt and nxt.sensor modules no longer exports name from sub-modules. In general, NXT-Python now avoids to have two names for the same object.

Output port constants are replaced by enumerations, using the enum module:

NXT-Python 2	NXT-Python 3
`PORT_A`	`Port.A`
`PORT_B`	`Port.B`
`PORT_C`	`Port.C`
`MODE_IDLE`	`Mode.IDLE`
`MODE_MOTOR_ON`	`Mode.ON`
`MODE_BRAKE`	`Mode.BRAKE`
`MODE_REGULATED`	`Mode.REGULATED`
`REGULATION_IDLE`	`RegulationMode.IDLE`
`REGULATION_MOTOR_SPEED`	`RegulationMode.SPEED`
`REGULATION_MOTOR_SYNC`	`RegulationMode.SYNC`
`RUN_STATE_IDLE`	`RunState.IDLE`
`RUN_STATE_RAMP_UP`	`RunState.RAMP_UP`
`RUN_STATE_RUNNING`	`RunState.RUNNING`
`RUN_STATE_RAMP_DOWN`	`RunState.RAMP_DOWN`

You can now create nxt.motor.Motor objects using nxt.brick.Brick.get_motor(), however direct creation still works.

Input port constants are replaced by enumerations, using the enum module. The nxt.sensor.common module has been removed, its content is directly available in nxt.sensor:

NXT-Python 2	NXT-Python 3
`PORT_1`	`Port.S1`
`PORT_2`	`Port.S2`
`PORT_3`	`Port.S3`
`PORT_4`	`Port.S4`
`Type.NO_SENSOR`	`Type.NO_SENSOR`
`Type.SWITCH`	`Type.SWITCH`
`Type.TEMPERATURE`	`Type.TEMPERATURE`
`Type.REFLECTION`	`Type.REFLECTION`
`Type.ANGLE`	`Type.ANGLE`
`Type.LIGHT_ACTIVE`	`Type.LIGHT_ACTIVE`
`Type.LIGHT_INACTIVE`	`Type.LIGHT_INACTIVE`
`Type.SOUND_DB`	`Type.SOUND_DB`
`Type.SOUND_DBA`	`Type.SOUND_DBA`
`Type.CUSTOM`	`Type.CUSTOM`
`Type.LOW_SPEED`	`Type.LOW_SPEED`
`Type.LOW_SPEED_9V`	`Type.LOW_SPEED_9V`
`Type.HIGH_SPEED`	`Type.HIGH_SPEED`
`Type.COLORFULL`	`Type.COLOR_FULL`
`Type.COLORRED`	`Type.COLOR_RED`
`Type.COLORGREEN`	`Type.COLOR_GREEN`
`Type.COLORBLUE`	`Type.COLOR_BLUE`
`Type.COLORNONE`	`Type.COLOR_NONE`
`Type.COLOREXIT`	`Type.COLOR_EXIT`
`Mode.RAW`	`Mode.RAW`
`Mode.BOOLEAN`	`Mode.BOOL`
`Mode.TRANSITION_CNT`	`Mode.EDGE`
`Mode.PERIOD_COUNTER`	`Mode.PULSE`
`Mode.PCT_FULL_SCALE`	`Mode.PERCENT`
`Mode.CELSIUS`	`Mode.CELSIUS`
`Mode.FAHRENHEIT`	`Mode.FAHRENHEIT`
`Mode.ANGLE_STEPS`	`Mode.ROTATION`
`Mode.MASK`	Removed
`Mode.MASK_SLOPE`	Removed

You can now create sensor objects using nxt.brick.Brick.get_sensor(), however direct creation still works. For digital sensors with identification information, this can automatically detect the sensor type as with previous version. The new cls argument allows creating a sensor object using another class.

Text String or Binary String

The NXT brick only understands ASCII, so this is the default encoding used in NXT-Python.

From nxt.brick.Brick:

get_device_info() now returns a str for the brick name.
file_write(), write_io_map() and message_write() now take bytes instead of a str.
file_read(), read_io_map() and poll_command() no longer return the read size, but the returned bytes object is cut to the right size.
get_current_program_name() returns a str.
file_delete() is fixed and returns a str.
find_files() and find_modules() use str for file and module names.

File Access

File reading and writing are now implemented using classes implementing io.RawIOBase. When using open_file(), depending of the parameters, the raw file-like object is returned directly, or wrapped in a io.BufferedIOBase or io.TextIOBase object.

Default access mode is now text with ASCII encoding, you need to ask explicitly for binary if needed.

This means that file access should be similar to regular Python file access.

Renamed

From nxt.brick.Brick:

delete() has been renamed to file_delete().
Many low level file and module access methods now have a file_ or module_ prefix. They are however not supposed to be used directly.

From nxt.error:

DirProtError and SysProtError have been renamed to DirectProtocolError and SystemProtocolError.
FileNotFound has been renamed to FileNotFoundError.
ModuleNotFound has been renamed to ModuleNotFoundError.
New EmptyMailboxError and NoActiveProgramError have been added as subclasses of DirectProtocolError.

Sensors:

nxt.sensor.generic.Color20 has been renamed to nxt.sensor.generic.Color.

Removed

Some attributes are now private (prefixed with _).

Support for the lightblue module has been removed. It has been integrated into PyBluez.

From nxt.brick:

Brick.open_read_linear() has been removed, it has never been accessible from outside the NXT brick.
File, FileReader and FileWriter have been removed, use Brick.open_file().
FileFinder has been removed, use Brick.find_files().
ModuleFinder has been removed, use Brick.find_modules().
Brick.mc has been removed, make an instance using:
```
mc = nxt.motcont.MotCont(the_brick)
```

From other modules:

nxt.motcont.MotCont.move_to() has been removed as it is not part of MotorControl interface and its role was not clear.
nxt.motcont.MotorConError has been removed and replaced with nxt.error.ProtocolError.
nxt.telegram.InvalidReplyError and nxt.telegram.InvalidOpcodeError have been removed and replaced with nxt.error.ProtocolError.

Module nxt.utils has been removed, use argparse.

Other Changes

From nxt.brick.Brick:

get_device_info() returns a tuple for the Bluetooth signal strength values instead of a single 32 bit value.
find_files() and find_modules() return an empty iterator instead of raising an exception when no file or module is found.
close() now closes the connection to the NXT brick. Also Brick now implements the context manager interface so that it can be used with the with syntax.
boot() now takes a argument to avoid accidental firmware erasure.

Other:

nxt.motcont.MotCont methods accept tuple as argument to control several ports.
Scripts command line interface has changed.