Learning Python [40]: Clever Use of Python’s PyQt5 and File for Chat Dialog

import sys

import datetime

from PyQt5.QtWidgets import (

QApplication, QMainWindow, QWidget, QVBoxLayout, QHBoxLayout,

QTextEdit, QPushButton, QLabel, QScrollArea

)

from PyQt5.QtCore import Qt, QDateTime

from PyQt5.QtGui import QTextCharFormat, QColor, QFont

class ChatWindow(QMainWindow):

def __init__(self):

super().__init__()

self.setWindowTitle(“Xiao Ming – Xiao Li Two-way Dialog Box”)

self.setMinimumSize(800, 600)

# Initialize file (create if it does not exist)

self.chat_file = “chat_record.txt”

with open(self.chat_file, “a”, encoding=”utf-8″) as f:

f.write(f”\n===== Dialogue Start: {QDateTime.currentDateTime().toString(‘yyyy-MM-dd HH:mm:ss’)} =====\n”)

# Create central component

central_widget = QWidget()

self.setCentralWidget(central_widget)

# Overall layout: left and right columns (Xiao Ming + Xiao Li)

main_layout = QHBoxLayout(central_widget)

main_layout.setSpacing(20)

main_layout.setContentsMargins(20, 20, 20, 20)

# 1. Create Xiao Ming’s chat area (saved as an instance property to avoid overwriting)

self.user_panel = self._create_chat_panel(“Xiao Ming”)

# 2. Create Xiao Li’s chat area (saved as an instance property)

self.client_panel = self._create_chat_panel(“Xiao Li”)

main_layout.addWidget(self.user_panel, stretch=1)

main_layout.addWidget(self.client_panel, stretch=1)

def _create_chat_panel(self, panel_name):

“””Create a single chat panel (title + chat display area + input area + send button)”””

panel = QWidget()

layout = QVBoxLayout(panel)

# Panel title

title_label = QLabel(panel_name)

title_label.setAlignment(Qt.AlignCenter)

title_label.setFont(QFont(“Microsoft YaHei”, 12, QFont.Bold))

layout.addWidget(title_label)

# Chat display area (read-only, with scroll)

display = QTextEdit()

display.setReadOnly(True)

display.setFont(QFont(“Microsoft YaHei”, 10))

display.setStyleSheet(“border: 1px solid #ccc; padding: 10px;”)

layout.addWidget(display, stretch=5)

# Input area + send button layout

input_layout = QHBoxLayout()

msg_input = QTextEdit()

msg_input.setPlaceholderText(“Enter message (send with Enter)”)

msg_input.setFont(QFont(“Microsoft YaHei”, 10))

msg_input.setMaximumHeight(100)

input_layout.addWidget(msg_input, stretch=4)

send_btn = QPushButton(“Send”)

send_btn.setStyleSheet(“background-color: #409EFF; color: white; border: none; padding: 8px;”)

# Bind send button: pass the current panel’s input box, display area, and name

send_btn.clicked.connect(lambda: self._send_message(panel_name, msg_input, display))

input_layout.addWidget(send_btn, stretch=1)

layout.addLayout(input_layout, stretch=1)

# Bind Enter to send (distinguish between normal Enter and Shift+Enter)

# Bind Enter event separately for each input box, passing panel information

def custom_key_press(event, input_box=msg_input, name=panel_name):

self._handle_enter(event, input_box, name)

msg_input.keyPressEvent = custom_key_press

# Bind properties to the panel (for easy access later)

panel.display = display

panel.input = msg_input

panel.name = panel_name

return panel

def _handle_enter(self, event, input_box, panel_name):

“””Handle Enter event: normal Enter sends, Shift+Enter creates a new line”””

if event.key() == Qt.Key_Return or event.key() == Qt.Key_Enter:

if event.modifiers() & Qt.ShiftModifier:

# Shift+Enter: normal new line

QTextEdit.keyPressEvent(input_box, event)

else:

# Normal Enter: send message (pass current input box)

self._send_message(panel_name, input_box, None)

else:

# Other keys are processed normally

QTextEdit.keyPressEvent(input_box, event)

def _send_message(self, sender_name, input_box, sender_display):

“””Core logic for sending messages: only display in the other party’s window + record to file”””

# Get the input message and trim whitespace

msg_content = input_box.toPlainText().strip()

if not msg_content:

return # Do not send empty messages

# Determine the receiving panel

if sender_name == “Xiao Ming”:

receiver_panel = self.client_panel # User sends → Xiao Li receives

sender_panel = self.user_panel # Sender’s own panel (for clearing input)

else:

receiver_panel = self.user_panel # Xiao Li sends → Xiao Ming receives

sender_panel = self.client_panel # Sender’s own panel

# Get the current time

current_time = QDateTime.currentDateTime().toString(“HH:mm:ss”)

# 1. Format message (distinguish sender, different colors)

sender_format = QTextCharFormat()

sender_format.setForeground(QColor(“#409EFF”) if sender_name == “Xiao Ming” else QColor(“#67C23A”))

sender_format.setFontWeight(QFont.Bold)

# ✅ Only display in the receiver’s window (left-aligned)

receiver_panel.display.append(f”\n【{sender_name} {current_time}】”)

receiver_panel.display.setTextCursor(receiver_panel.display.textCursor())

receiver_panel.display.setCurrentCharFormat(sender_format)

receiver_panel.display.insertPlainText(msg_content)

receiver_panel.display.setAlignment(Qt.AlignLeft)

# 2. Record to file

with open(self.chat_file, “a”, encoding=”utf-8″) as f:

f.write(f”[{current_time}] {sender_name}：{msg_content}\n”)

# 3. Clear the sender’s input box

input_box.clear()

# 4. Scroll the receiver’s window to the latest message

receiver_panel.display.verticalScrollBar().setValue(

receiver_panel.display.verticalScrollBar().maximum()

)

if __name__ == “__main__”:

app = QApplication(sys.argv)

window = ChatWindow()

window.show()

sys.exit(app.exec_())