问题
I wrote a simple Tkinter based Python application that reads text from a serial connection and adds it to the window, specifically a text widged.
After a lot of tweaks and some very strange exceptions, this works. Then I added autoscrolling by doing this:
self.text.insert(END, str(parsed_line))
self.text.yview(END)
These lines run in a thread. The thread blocks on reading fromt the serial connection, splits lines and then adds all lines to the widget.
This works, too. Then I wanted to allow the user to scroll which should disable auto-scroll until the user scrolls back to the bottom.
I found this Stop Text widget from scrolling when content is changed which seems to be related. Especially, I tried the code from DuckAssasin's comment:
if self.myWidgetScrollbar.get() == 1.0:
self.myWidget.yview(END)
I also tried .get()[1] which is actually the element I want (bottom position). However, this crashes with the following exception:
Traceback (most recent call last):
File "transformer-gui.py", line 119, in run
pos = self.scrollbar.get()[1]
File "C:\Python26\lib\lib-tk\Tkinter.py", line 2809, in get
return self._getdoubles(self.tk.call(self._w, 'get'))
File "C:\Python26\lib\lib-tk\Tkinter.py", line 1028, in _getdoubles
return tuple(map(getdouble, self.tk.splitlist(string)))
ValueError: invalid literal for float(): None
It seems as if tkinter somewhere returns None which then is being parsed as a float. I read somewhere, that e.g. the index method of the text widged sometimes returnes None if the requested location is not visible.
Hopefully, anybody can help me out with this problem!
[EDIT]
Ok, I have assembled a demo script that can reproduce this issue on my Win XP machine:
import re,sys,time
from Tkinter import *
import Tkinter
import threading
import traceback
class ReaderThread(threading.Thread):
def __init__(self, text, scrollbar):
print "Thread init"
threading.Thread.__init__(self)
self.text = text
self.scrollbar = scrollbar
self.running = True
def stop(self):
print "Stopping thread"
running = False
def run(self):
print "Thread started"
time.sleep(5)
i = 1
try:
while(self.running):
# emulating delay when reading from serial interface
time.sleep(0.05)
line = "the quick brown fox jumps over the lazy dog\n"
curIndex = "1.0"
lowerEdge = 1.0
pos = 1.0
# get cur position
pos = self.scrollbar.get()[1]
# Disable scrollbar
self.text.configure(yscrollcommand=None, state=NORMAL)
# Add to text window
self.text.insert(END, str(line))
startIndex = repr(i) + ".0"
curIndex = repr(i) + ".end"
# Perform colorization
if i % 6 == 0:
self.text.tag_add("warn", startIndex, curIndex)
elif i % 6 == 1:
self.text.tag_add("debug", startIndex, curIndex)
elif i % 6 == 2:
self.text.tag_add("info", startIndex, curIndex)
elif i % 6 == 3:
self.text.tag_add("error", startIndex, curIndex)
elif i % 6 == 4:
self.text.tag_add("fatal", startIndex, curIndex)
i = i + 1
# Enable scrollbar
self.text.configure(yscrollcommand=self.scrollbar.set, state=DISABLED)
# Auto scroll down to the end if scroll bar was at the bottom before
# Otherwise allow customer scrolling
if pos == 1.0:
self.text.yview(END)
#if(lowerEdge == 1.0):
# print "is lower edge!"
#self.text.see(curIndex)
#else:
# print "Customer scrolling", lowerEdge
# Get current scrollbar position before inserting
#(upperEdge, lowerEdge) = self.scrollbar.get()
#print upperEdge, lowerEdge
#self.text.update_idletasks()
except Exception as e:
traceback.print_exc(file=sys.stdout)
print "Exception in receiver thread, stopping..."
pass
print "Thread stopped"
class Transformer:
def __init__(self):
pass
def start(self):
"""starts to read linewise from self.in_stream and parses the read lines"""
count = 1
root = Tk()
root.title("Tkinter Auto-Scrolling Test")
topPane = PanedWindow(root, orient=HORIZONTAL)
topPane.pack(side=TOP, fill=X)
lowerPane = PanedWindow(root, orient=VERTICAL)
scrollbar = Scrollbar(root)
scrollbar.pack(side=RIGHT, fill=Y)
text = Text(wrap=WORD, yscrollcommand=scrollbar.set)
scrollbar.config(command=text.yview)
# Color definition for log levels
text.tag_config("debug",foreground="gray50")
text.tag_config("info",foreground="green")
text.tag_config("warn",foreground="orange")
text.tag_config("error",foreground="red")
text.tag_config("fatal",foreground="#8B008B")
# set default color
text.config(background="black", foreground="gray");
text.pack(expand=YES, fill=BOTH)
lowerPane.add(text)
lowerPane.pack(expand=YES, fill=BOTH)
t = ReaderThread(text, scrollbar)
print "Starting thread"
t.start()
try:
root.mainloop()
except Exception as e:
print "Exception in window manager: ", e
t.stop()
t.join()
if __name__ == "__main__":
try:
trans = Transformer()
trans.start()
except Exception as e:
print "Error: ", e
sys.exit(1)
I let this scipt run and start to scroll up and down and after some time I get a lot of always different exceptions such as:
.\source\testtools\device-log-transformer>python tkinter-autoscroll.py
Thread init
Starting thread
Thread started
Traceback (most recent call last):
File "tkinter-autoscroll.py", line 59, in run
self.text.configure(yscrollcommand=self.scrollbar.set, state=DISABLED)
File "C:\Python26\lib\lib-tk\Tkinter.py", line 1202, in configure
Stopping thread
return self._configure('configure', cnf, kw)
File "C:\Python26\lib\lib-tk\Tkinter.py", line 1193, in _configure
self.tk.call(_flatten((self._w, cmd)) + self._options(cnf))
TclError: invalid command name ".14762592"
Exception in receiver thread, stopping...
Thread stopped
.\source\testtools\device-log-transformer>python tkinter-autoscroll.py
Thread init
Starting thread
Thread started
Stopping thread
Traceback (most recent call last):
File "tkinter-autoscroll.py", line 35, in run
pos = self.scrollbar.get()[1]
File "C:\Python26\lib\lib-tk\Tkinter.py", line 2809, in get
return self._getdoubles(self.tk.call(self._w, 'get'))
TclError: invalid command name ".14762512"
Exception in receiver thread, stopping...
Thread stopped
.\source\testtools\device-log-transformer>python tkinter-autoscroll.py
Thread init
Starting thread
Thread started
Traceback (most recent call last):
File "tkinter-autoscroll.py", line 65, in run
self.text.yview(END)
File "C:\Python26\lib\lib-tk\Tkinter.py", line 3156, in yview
self.tk.call((self._w, 'yview') + what)
Stopping threadTclError: invalid command name ".14762592"
Exception in receiver thread, stopping...
Thread stopped
.\source\testtools\device-log-transformer>python tkinter-autoscroll.py
Thread init
Starting thread
Thread started
Traceback (most recent call last):
File "tkinter-autoscroll.py", line 35, in run
pos = self.scrollbar.get()[1]
File "C:\Python26\lib\lib-tk\Tkinter.py", line 2809, in get
return self._getdoubles(self.tk.call(self._w, 'get'))
File "C:\Python26\lib\lib-tk\Tkinter.py", line 1028, in _getdoubles
return tuple(map(getdouble, self.tk.splitlist(string)))
ValueError: invalid literal for float(): None
Exception in receiver thread, stopping...
Thread stopped
Stopping thread
.\source\testtools\device-log-transformer>python tkinter-autoscroll.py
Thread init
Starting thread
Thread started
Traceback (most recent call last):
File "tkinter-autoscroll.py", line 53, in run
self.text.tag_add("error", startIndex, curIndex)
File "C:\Python26\lib\lib-tk\Tkinter.py", line 3057, in tag_add
(self._w, 'tag', 'add', tagName, index1) + args)
TclError: bad option "261.0": must be bbox, cget, compare, configure, count, debug, delete, dlineinfo, dump, edit, get, image, index, insert, mark, pe
er, replace, scan, search, see, tag, window, xview, or yview
Exception in receiver thread, stopping...
Thread stopped
I hope this helps you to help me :)
Thanks,
/J
回答1:
It's hard to tell what's really going on but have you considered using a Queue?
from Tkinter import *
import time, Queue, thread
def simulate_input(queue):
for i in range(100):
info = time.time()
queue.put(info)
time.sleep(0.5)
class Demo:
def __init__(self, root, dataQueue):
self.root = root
self.dataQueue = dataQueue
self.text = Text(self.root, height=10)
self.scroller = Scrollbar(self.root, command=self.text.yview)
self.text.config(yscrollcommand=self.scroller.set)
self.text.tag_config('newline', background='green')
self.scroller.pack(side='right', fill='y')
self.text.pack(fill='both', expand=1)
self.root.after_idle(self.poll)
def poll(self):
try:
data = self.dataQueue.get_nowait()
except Queue.Empty:
pass
else:
self.text.tag_remove('newline', '1.0', 'end')
position = self.scroller.get()
self.text.insert('end', '%s\n' %(data), 'newline')
if (position[1] == 1.0):
self.text.see('end')
self.root.after(1000, self.poll)
q = Queue.Queue()
root = Tk()
app = Demo(root, q)
worker = thread.start_new_thread(simulate_input, (q,))
root.mainloop()
回答2:
Regarding your demo script.
You're doing GUI stuff from the non-GUI thread. That tends to cause problems.
see: http://www.effbot.org/zone/tkinter-threads.htm
回答3:
OK,
based on the valuable suggestions by noob oddy I was able to rewrite the example script by using the Tkinter.generate_event() method to generate asynchronous event and a queue to pass the information.
Every time a line is read from the stream (which is simulated by a constant string and a delay), I append the line to a queue (because passing objects to the event method is not supported AFAIK) and then create a new event.
The event callback method retrieves the message from the queue and adds it to the Text widged. This works because this method is called from the Tkinter mainloop an thus it cannot interfere with the other jobs.
Here is the script:
import re,sys,time
from Tkinter import *
import Tkinter
import threading
import traceback
import Queue
class ReaderThread(threading.Thread):
def __init__(self, root, queue):
print "Thread init"
threading.Thread.__init__(self)
self.root = root
self.running = True
self.q = queue
def stop(self):
print "Stopping thread"
running = False
def run(self):
print "Thread started"
time.sleep(5)
try:
while(self.running):
# emulating delay when reading from serial interface
time.sleep(0.05)
curline = "the quick brown fox jumps over the lazy dog\n"
try:
self.q.put(curline)
self.root.event_generate('<<AppendLine>>', when='tail')
# If it failed, the window has been destoyed: over
except TclError as e:
print e
break
except Exception as e:
traceback.print_exc(file=sys.stdout)
print "Exception in receiver thread, stopping..."
pass
print "Thread stopped"
class Transformer:
def __init__(self):
self.q = Queue.Queue()
self.lineIndex = 1
pass
def appendLine(self, event):
line = self.q.get_nowait()
if line == None:
return
i = self.lineIndex
curIndex = "1.0"
lowerEdge = 1.0
pos = 1.0
# get cur position
pos = self.scrollbar.get()[1]
# Disable scrollbar
self.text.configure(yscrollcommand=None, state=NORMAL)
# Add to text window
self.text.insert(END, str(line))
startIndex = repr(i) + ".0"
curIndex = repr(i) + ".end"
# Perform colorization
if i % 6 == 0:
self.text.tag_add("warn", startIndex, curIndex)
elif i % 6 == 1:
self.text.tag_add("debug", startIndex, curIndex)
elif i % 6 == 2:
self.text.tag_add("info", startIndex, curIndex)
elif i % 6 == 3:
self.text.tag_add("error", startIndex, curIndex)
elif i % 6 == 4:
self.text.tag_add("fatal", startIndex, curIndex)
i = i + 1
# Enable scrollbar
self.text.configure(yscrollcommand=self.scrollbar.set, state=DISABLED)
# Auto scroll down to the end if scroll bar was at the bottom before
# Otherwise allow customer scrolling
if pos == 1.0:
self.text.yview(END)
self.lineIndex = i
def start(self):
"""starts to read linewise from self.in_stream and parses the read lines"""
count = 1
self.root = Tk()
self.root.title("Tkinter Auto-Scrolling Test")#
self.root.bind('<<AppendLine>>', self.appendLine)
self.topPane = PanedWindow(self.root, orient=HORIZONTAL)
self.topPane.pack(side=TOP, fill=X)
self.lowerPane = PanedWindow(self.root, orient=VERTICAL)
self.scrollbar = Scrollbar(self.root)
self.scrollbar.pack(side=RIGHT, fill=Y)
self.text = Text(wrap=WORD, yscrollcommand=self.scrollbar.set)
self.scrollbar.config(command=self.text.yview)
# Color definition for log levels
self.text.tag_config("debug",foreground="gray50")
self.text.tag_config("info",foreground="green")
self.text.tag_config("warn",foreground="orange")
self.text.tag_config("error",foreground="red")
self.text.tag_config("fatal",foreground="#8B008B")
# set default color
self.text.config(background="black", foreground="gray");
self.text.pack(expand=YES, fill=BOTH)
self.lowerPane.add(self.text)
self.lowerPane.pack(expand=YES, fill=BOTH)
t = ReaderThread(self.root, self.q)
print "Starting thread"
t.start()
try:
self.root.mainloop()
except Exception as e:
print "Exception in window manager: ", e
t.stop()
t.join()
if __name__ == "__main__":
try:
trans = Transformer()
trans.start()
except Exception as e:
print "Error: ", e
sys.exit(1)
Thanks again to everybody who contributed for your help!
来源：https://stackoverflow.com/questions/8850329/python-tkinter-text-widget-with-auto-custom-scroll