Serial Port As Global

[Prasanjith]

How do I define the selected port as global so I can call it anywhere in my code.

In below code I have selecting the serial port inside a function.SO I cannot use it anywhere in my code.

How can I make it as global?

import tkinter as tk import tkinter.ttk as ttk import serial.tools.list_ports import serial import time # --- main --- root = tk.Tk() #This is our label label = ttk.Label(root, text = "Please Select a COM PORT") label.grid(column = 1, row = 4) label.pack() #Functions def on_select(event=None): # get selection from event print("event.widget:", event.widget.get()) # or get selection directly from combobox print("comboboxes: ", cb.get()) val = cb.get() label.configure(text= val[:5]) selected_COM = val[:5] #==================== # create a serial object selected_COM = val[:5] ser = serial.Serial(selected_COM) # replace 'COM1' with the name of your serial port ser.baudrate = 9600 ser.bytesize=8 ser.parity ='N' # No parity ser.stopbits = 1 # Number of Stop bits = 1 time.sleep(3) #ser.write(b"A") #transmit 'A' (8bit) to micro/Arduino #ser.close() # Close the port #===================== cb = ttk.Combobox(root, values=serial_ports()) cb.pack() label2 = ttk.Label(root, text = "Please Insert a Number") label2.pack() # assign function to combobox cb.bind('<<ComboboxSelected>>', on_select) 

[menator01]

You might could do something like this.

# Do the imports import serial from serial.tools import list_ports import tkinter as tk from tkinter import ttk # Get ports ports = list_ports.comports() # Function for getting and displaying port data def getdata(com, frame): # Get port name data = serial.Serial(com.get()) # Set index to 0 for looping index = 0 # Get item data in ther serial port return data # Place in tkinter labels for key, value in data.__dict__.items(): label = tk.Label(frame, text=f'{key.strip("_").upper()}:', anchor='w', relief='groove') label2 = tk.Label(frame, text=value, anchor='w', relief='groove') label.grid(column=0, row=index, sticky='new') label2.grid(column=1, row=index, sticky='new') index += 1 # Start tkinter root = tk.Tk() root.columnconfigure(0, weight=1) root['padx'] = 5 root['pady'] = 8 # Create a string variable and set default value var = tk.StringVar() var.set('COM1') # Create a frame to hold display data frame = tk.Frame(root) frame.grid(column=0, row=1, sticky='news', pady=5) # Create and populate a combobox combobox = ttk.Combobox(root, values=ports, width=80) combobox.grid(columnspan=2, column=0, row=0, sticky='new') combobox['state'] = 'readonly' # Set current value for combobox combobox.current(0) # Bind combobox to function combobox.bind('<<ComboboxSelected>>', lambda _: getdata(var, frame)) # Uncomment for data to pull up on opening window # getdata(var, frame) root.mainloop() 

[deanhystad]

I think the best solution is to use classes. This example makes Window class that is a Tk that knows about serial ports. It is a subclass of tkinter.Tk, so making a Window is similar to "root=Tk()".

import tkinter as tk import tkinter.ttk as ttk from serial import Serial from serial.tools import list_ports class Window(tk.Tk): def __init__(self, *args, **kwargs): super().__init__(*args, **kwargs) self.label = tk.Label(self) ports = [port.name for port in list_ports.comports()] if not ports: quit("There are no serial ports on this device.") self.serial_ports = ttk.Combobox(self, values=ports, width=7) self.serial_ports.bind("<<ComboboxSelected>>", self.select_serial_port) self.serial_port = None self.serial_ports.set(ports[0]) self.send_ab = tk.Button(self, text="write('A')", command=self.writea()) self.serial_ports.pack(padx=50, pady=(50, 0)) self.send_ab.pack(pady=(10, 50)) def select_serial_port(self, _): """Select serial port from available ports.""" if self.serial_port: self.serial_port.close() self.serial_port = Serial( self.serial_ports.get(), baudrate=9600, bytesize=8, parity="N", stopbits=1 ) self.serial_port.close() def writea(self): """write 'A' out the serial port.""" if self.serial_port: self.serial_port.open() self.serial_port.write(b"A") self.serial_port.close() Window().mainloop()

One of the neat things about classes, is they give you a new namespace. You are already familiar with the global and local namespaces. An assignment made in the local namespace will not be visible in the global namespace (the source of your problem) unless you use the "global" keyword. Classes let you make additional namespaces. When I create an instance of "Window", this not only creates an object, it also creates a new namespace that only exists inside that object. Things added to the "instance namespace" will exist as long as the instance does. This lets me assign an instance variable in one method and use it in another. That is used in Window to make a "serial_port" in the "select_serial_port()" method, and use that same serial port in the "writea()" method. Very useful.