python - redirect stdout to tkinter text widget

Question

I'm trying to redirect the stdout of a function to a tkinter text widget. The problem I am running into is that it writes each line to a new window instead of listing everything in one. The function scans a directory and lists any file that is 0k. If no files are 0k it prints that. So, the problem is that if there are 30 0k files in a directory, it will open 30 windows with a single line in each. Now, I know what the problem is. If you look in my function code Zerok() I am telling it:

if os.stat(filename).st_size==0:  
       redirector(filename)

I know that every time os.stat sees a file that is 0k it is then sending that to redirector, that's why its a new window for each file. I just have no idea how to fix it. Complete code below. Thanks for the help.

import Tkinter
from Tkinter import *
import tkFileDialog

class IORedirector(object):
    '''A general class for redirecting I/O to this Text widget.'''
    def __init__(self,text_area):
        self.text_area = text_area

class StdoutRedirector(IORedirector):
    '''A class for redirecting stdout to this Text widget.'''
    def write(self,str):
        self.text_area.write(str,False)

def redirector(inputStr):
    import sys
    root = Tk()
    sys.stdout = StdoutRedirector(root)
    T = Text(root)
    T.pack()
    T.insert(END, inputStr)

####This Function checks a User defined directory for 0k files
def Zerok():
    import os
    sys.stdout.write = redirector #whenever sys.stdout.write is called, redirector is called.
    PATH = tkFileDialog.askdirectory(initialdir="/",title='Please select a directory')  
    for root,dirs,files in os.walk(PATH):  
     for name in files:  
      filename=os.path.join(root,name)  
      if os.stat(filename).st_size==0:  
       redirector(filename)
      else:
          redirector("There are no empty files in that Directory")
          break

#############################Main GUI Window###########################
win = Tk()
f = Frame(win)
b1 = Button(f,text="List Size")
b2 = Button(f,text="ZeroK")
b3 = Button(f,text="Rename")
b4 = Button(f,text="ListGen")
b5 = Button(f,text="ListDir")
b1.pack()
b2.pack()
b3.pack()
b4.pack()
b5.pack()
l = Label(win, text="Select an Option")
l.pack()
f.pack()
b2.configure(command=Zerok)
win.mainloop()

Bryan Oakley Bryan Oakley · Accepted Answer · 2016-04-13T17:44:39

The fix is simple: don't create more than one redirector. The whole point of the redirector is that you create it once, and then normal print statements will show up in that window.

You'll need to make a couple of small changes to your redirector function. First, it shouldn't call Tk; instead, it should create an instance of Toplevel since a tkinter program must have exactly one root window. Second, you must pass a text widget to IORedirector since it needs to know the exact widget to write to.

def redirector(inputStr=""):
    import sys
    root = Toplevel()
    T = Text(root)
    sys.stdout = StdoutRedirector(T)
    T.pack()
    T.insert(END, inputStr)

Next, you should only call this function a single time. From then on, to have data appear in the window you would use a normal print statement.

You can create it in the main block of code:

win = Tk()
...
r = redirector()
win.mainloop()

Next, you need to modify the write function, since it must write to the text widget:

class StdoutRedirector(IORedirector):
    '''A class for redirecting stdout to this Text widget.'''
    def write(self,str):
        self.text_area.insert("end", str)

Finally, change your Zerok function to use print statements:

def Zerok(): ... if os.stat(filename).st_size==0:
print(filename) else: print("There are no empty files in that Directory") break

python - redirect stdout to tkinter text widget

2 Answers