chatapp.py

import sys, os
from PyQt5.QtCore import *
from PyQt5.QtWidgets import *
from requests import Session
from threading import Thread
from time import sleep
from pubnub.callbacks import SubscribeCallback
from pubnub.enums import PNStatusCategory
from pubnub.pnconfiguration import PNConfiguration
from pubnub.pubnub import PubNub

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## PubNub Messaging Setup
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channel = 'chat-channel'
pnconfig = PNConfiguration()

pnconfig.publish_key = '__YOUR_PUBNUB_PUBLISH_KEY_HERE__'
pnconfig.subscribe_key = '__YOUR_PUBNUB_SUBSCRIBE_KEY_HERE__'

pubnub = PubNub(pnconfig)
new_messages = []

def pubnub_publish(data):
    pubnub.publish().channel(channel).message(data).sync()

class MySubscribeCallback(SubscribeCallback):
    def message(self, pubnub, pn_message):
        print('incoming_message', pn_message.message)
        new_messages.append(pn_message.message)

def format_message(message_body):
    return message_body.get('name') + ": " + message_body.get('message')

pubnub.add_listener(MySubscribeCallback())
pubnub.subscribe().channels(channel).execute()


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## GUI Setup
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def exit_handler():
    os._exit(1)

app = QApplication([])
app.aboutToQuit.connect(exit_handler)
text_area = QPlainTextEdit()
text_area.setFocusPolicy(Qt.NoFocus)
message_input = QLineEdit()
message_input.setMaxLength(1000) # max character length of a chat message
layout = QVBoxLayout()
layout.addWidget(text_area)
layout.addWidget(message_input)
window = QWidget()
window.setLayout(layout)
window.show()


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## Username Input
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name, okPressed = QInputDialog.getText(
    window,
    "Username input",
    "Input your chat username",
    QLineEdit.Normal,
    ""
)

if okPressed and name != '' and len(name) < 20:
    print('Username:', name)
else:
    exit_handler() # invalid username, exiting


##-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
## UI Send/Receive Message Functions
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def display_new_messages():
    while new_messages:
        if len(new_messages) > 0:
            msg = new_messages.pop(0)
            msg = format_message(msg)
            text_area.appendPlainText(msg)

def send_message():
    pubnub_publish({"name": name, "message": message_input.text()})
    message_input.clear()


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## Qt Signals
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message_input.returnPressed.connect(send_message)
timer = QTimer()
timer.timeout.connect(display_new_messages)
timer.start(1000)

sys.exit(app.exec_())