python_channel

Description:

python channel

python_channel #
With this plugin developers can use python in there flutter applications on windows.
requirements #

python +3.7
flutter_channel python package, install it from PyPi.

how does it work? #
This plugin depends on unix sockets (TCP) protocol.
how to use? #
1. bind the hosts #
First thing you have to bind the hosts by calling PythonChannelPlugin.bindHost() this method take 4 parameters name,debugPyPath,debugExePath,releasePath, You can bind multi hosts.
name is unique name for the host
debugPyPath it is the absolute path of the main python file. The plugin will use it to start the host in debug mode if debugExePath is not set.
debugExePath it is the absolute path of the main executable file. You need to use is to debug the compiled file from python.
releasePath it is the relative path of the main executable file. in release mode you have to put the executable compiled file side by side with the application files see the example on github
host example
PythonChannelPlugin.bindHost(
name: 'host',
debugExePath:
'E:\\projects\\python_channel\\flutter_channel\\dist\\example.exe',
debugPyPath: 'E:\\projects\\python_channel\\flutter_channel\\example.py',
releasePath: 'main.exe');
copied to clipboard
where put the executable file in release mode?
release-app/
data/
app.exe # the executable file for the flutter app
main.exe # the executable file that compiled from python
...
copied to clipboard
2. create channels and bind it to host #
There is number of built in channel types to use like: BytesChannel,JsonChannel, StringChannel and MethodChannel, after you create the channel you have to bind it to host using PythonChannelPlugin.bindChannel() this method take two parameters first one is name is the name of the host and second one is channel.
channels examples

BytesChannel bytesChannel = BytesChannel(name: 'channel1');
StringChannel stringChannel = StringChannel(name: 'channel2');
JsonChannel jsonChannel = JsonChannel(name: 'channel3');
MethodChannel methodChannel = MethodChannel(name: 'channel4');
// bind channels
PythonChannelPlugin.bindChannel('host', bytesChannel);
PythonChannelPlugin.bindChannel('host', stringChannel);
PythonChannelPlugin.bindChannel('host', jsonChannel);
PythonChannelPlugin.bindChannel('host', methodChannel);

copied to clipboard
3. set channel handler #
The handler of the channel is a function that receive the messages that is sent to the channel, Each handler should take tow parameters message and reply.
message is the first parameter and it is the massage that was received and it's type depends on the channel type see the following table.



Channel Type
Channel Output




BytesChannel
Uint8List


StringChannel
String


JsonChannel
Object


MethodChannel
depends on reply that comes from python can be any primitive type like int ,String,bool or List


custom channel
depends on the implement of the encodeOutput and decodeOutput methods



reply is the second parameter, it is instance of Reply you should use this object to send reply on the received message, You can reply with another message or reply with null.
Your reply will not be sent to the channel handler in the python side. It will be send to the reply call back that used with send method in python side.
handler example
stringChannel.setHandler(
(message, reply) {
print(message);
reply.reply('hi python');
},
);
copied to clipboard
4. send message #
You can send message using send method from the channel object. It take one parameter msg and the parameter type depends on the channel type see the following table.



Channel Type
Channel Input




BytesChannel
Uint8List


StringChannel
String


JsonChannel
Object


MethodChannel
MethodCall


custom channel
depends on the implement of the encodeInput and decodeInput methods



this method is Future that will keep wait until reply comes back.
send example
stringChannel.send('hello world').then((reply) => print(reply));

methodChannel.invokeMethod('sayHello', {"name": 'ghale'})
.then((reply) => print(reply));
copied to clipboard
5. get channel #
You can access bound channel from anywhere using PythonChannelPlugin.getChannel(), This method take two parameters the hostName and channelName
get channel example
MethodChannel helloChannel = PythonChannelPlugin.getChannel('sayHello', 'sayHi') as MethodChannel;
copied to clipboard
6. unbind host #
You can unbind host by calling PythonChannelPlugin.unbindHost(), This method take one parameter, that parameter is the host name. When unbind host the host process will be killed with it's all channels.
unbind host example
PythonChannelPlugin.unbindHost('sayHello');
copied to clipboard
MethodChannel #
There is some notes we have to mention to about MethodChannel usage.
1. catch exception #
If channel handler in python side raise PythonChannelMethodException you can catch it in dart side
methodChannel.invokeMethod('sayHello', {"name": 'ghale'})
.then((reply) => print(reply))
.catchError((e){});
//or
try{
await methodChannel.invokeMethod('sayHello', {"name": 'ghale'});
}catch(e){

}
copied to clipboard
2. throw exception in the handler
You can throw PythonChannelMethodException in the handler this exception will be sent by the channel and will pass to the second parameter of the reply call back in python side.
create your own channel type #
You can create your own channel by write class that inherit Channel generic class.
You should implement 4 method encodeInput, encodeOutput ,decodeInput and decodeOutput
and set the input/output types using the generic class.

encodeInput convert the input of the channel from Uint8List
encodeOutput convert the output of the channel from Uint8List
decodeInput convert the input of the channel to Uint8List
decodeOutput convert the input of the channel to Uint8List
where the input is what the channel send and the output is what the channel receive

release mode #
in release mode you have to compile your main python file to an executable file, We recommend you to use PyInstaller.
Note: you have to build the executable file with console otherwise the package will not work