如何防止pyqt中的textEdit更改

Question

how to prevent textEdit in pyqt from changing when to many characters are entered? can not find setting qt designer to limit number of characters, or limit auto resizing of box.
tried:

self.ui.textEdit_45.setFixedSize(30,  30)

set the minimium and maximium to width 30, height 30
sizePolicy [Fixed, Fixed, 0, 0]
did not work

if more than 2 characters are entered, the box gets 2 x's at top right and bottom left, and can not make out what is in the box.

Answer 1

An idea would be to count the character the textEdit has QTextEdit.toPlainText() every time the text changes self.textEdit.textChanged.connect() . If the number of character makes the QTextEdit deforme, make appear like the input it's disabled by slicing the input.

MWE:

from PyQt4 import  QtGui, QtCore
import sys

class MWindow(QtGui.QMainWindow):

    TwoDigits = 2 # Maximum number of characters allowed

    def __init__(self):
        QtGui.QWidget.__init__(self)
        self.setGeometry(300, 300, 250, 150)
        #define QTextEdit
        self.TE = QtGui.QTextEdit(self)
        self.TE.setGeometry(0,0, 30,30)

        self.TE.textChanged.connect(self.Limiter)

    def Limiter(self):
        NumChar = len( self.TE.toPlainText() )
        # according to geometry 2 characters is enough, so enter if over TwoDigits
        if NumChar > self.TwoDigits:
            Text = self.TE.toPlainText() # get text
            Text = Text[:self.TwoDigits] # slice first TwoDigits
            print(Text) # debugging
            self.TE.setPlainText(Text) # set sliced text
            self.TE.moveCursor(QtGui.QTextCursor.End) # move cursor to end, like if nothing happens

app = QtGui.QApplication([sys.argv])
win = MWindow()
win.show()
sys.exit(app.exec_())