python - Tkinter - How can I write Tkinter reg. expression to fetch the string after a word?

Question

[PROBLEM] How can I write Tkinter reg. expression to fetch the string after a word ?

[INPUT]

def addCutOffFromButton():
        fieldText = afterCutOff.get()
        searchText =  '[cut\-off:.*]'
        replaceText = 'cut-off:' + str(fieldText)
        startPosition = textPad.search(searchText, "1.0", stopindex=END, regexp=True)
        print "startPosition", '{!r}'.format(startPosition)
        print len(searchText)
        if startPosition:
            endPosition = '{}+{}c'.format(startPosition, len(searchText))
            print "endPosition", '{!r}'.format(endPosition)
            textPad.delete (startPosition, endPosition)
            textPad.insert (startPosition, replaceText)
        else:
            textPad.insert(END+'-1c', '\n' + 'cut-off:' + str(fieldText))

[OUTPUT]

This code will replace: "cut-off: xyz" if:
- there is no text before "cut-off: xyz"
- there is text before "cut-off: xyz" but that text does not include the chars from "cut-off: xyz"

[DESIRED] - the code should replace "cut-off: xyz" regardless of its position

[NOTE] - If i replace the reg exp with static string ("cut-off"), then I will not face any problems - python regular expression: "(cut-off.*)" will not deliver expected output

The first part of the question asks about finding text after a word, but later in the question you mention replacing text. Are you wanting to get the word after a pattern, or replace a word after a pattern, or replace the pattern? Also, are the brackets literally part of what you're searching for, or is that an attempt at writing a regular expression? It's not clear what you want. — Bryan Oakley
– Bryan Oakley, Commented Oct 22, 2015 at 14:58
Hi. there are 2 main parts: find a text and replace it by other text. I created the question related to reg exp because this is the root cause for my problem. As I mentioned, If i replace the reg exp with static string ("cut-off"), then I will not face any problems — george
– george, Commented Oct 22, 2015 at 19:47

Bryan Oakley · Accepted Answer · 2015-10-22 15:10:43Z

1

The tkinter text widget search function can only return what it finds, and how many characters it found. It can search via a regular expression, but it can't return individual groups from within that expression such as the text after a word.

The regular expression syntax is close to the normal python regular expression syntax, but it's not identical. The syntax is documented on the tcl/tk re_syntax man page.

The search mechanism will return the index of a match. It can optionally return the number of characters matched, which makes it possible to select everything that matched.

For example, if you want to replace everything that begins with "cut-off: ", you can do something like this:

import tkinter as tk
...
countVar = tk.IntVar()
startPosition = textPad.search(r'cut-off: .*', "1.0", count=countVar, regexp=True)
textPad.delete(startPosition, "%s+%sc" % (startPosition, countVar.get()))
textPad.insert(startPosition, replaceText)

answered Oct 22, 2015 at 15:10

Bryan Oakley

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3 Comments

george Over a year ago

I tried your suggestion. The python idle returned: "Exception in Tkinter callback Traceback (most recent call last): File "C:\Python27\lib\lib-tk\Tkinter.py", line 1536, in call return self.func(*args) File "C:\automat\test", line 377, in addCutOffFromButton textPad.delete(startPosition, "%s+%sc" % (startPosition, countVar.get())) File "C:\Python27\lib\lib-tk\Tkinter.py", line 2971, in delete self.tk.call(self._w, 'delete', index1, index2) TclError: bad text index """. \n. note: I use python 2.7.10. I will keep investigating....

Bryan Oakley Over a year ago

@user3438538: if the index is "", it didn't find the pattern.

george Over a year ago

thanks Bryan for helping me out. I spotted out the problem. there was a bonus white space after the colon. status: problem solved

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