"""Basic regular expression demostration facility (Perl style syntax).""" from Tkinter import *import re class ReDemo:     def __init__(self, master):        self.master = master         self.promptdisplay = Label(self.master, anchor=W,                text="Enter a Perl-style regular expression:")        self.promptdisplay.pack(side=TOP, fill=X)         self.regexdisplay = Entry(self.master)        self.regexdisplay.pack(fill=X)        self.regexdisplay.focus_set()         self.addoptions()         self.statusdisplay = Label(self.master, text="", anchor=W)        self.statusdisplay.pack(side=TOP, fill=X)         self.labeldisplay = Label(self.master, anchor=W,                text="Enter a string to search:")        self.labeldisplay.pack(fill=X)        self.labeldisplay.pack(fill=X)         self.showframe = Frame(master)        self.showframe.pack(fill=X, anchor=W)         self.showvar = StringVar(master)        self.showvar.set("first")         self.showfirstradio = Radiobutton(self.showframe,                                         text="Highlight first match",                                          variable=self.showvar,                                          value="first",                                          command=self.recompile)        self.showfirstradio.pack(side=LEFT)         self.showallradio = Radiobutton(self.showframe,                                        text="Highlight all matches",                                        variable=self.showvar,                                        value="all",                                        command=self.recompile)        self.showallradio.pack(side=LEFT)         self.stringdisplay = Text(self.master, width=60, height=4)        self.stringdisplay.pack(fill=BOTH, expand=1)        self.stringdisplay.tag_configure("hit", background="yellow")         self.grouplabel = Label(self.master, text="Groups:", anchor=W)        self.grouplabel.pack(fill=X)         self.grouplist = Listbox(self.master)        self.grouplist.pack(expand=1, fill=BOTH)         self.regexdisplay.bind('<Key>', self.recompile)        self.stringdisplay.bind('<Key>', self.reevaluate)         self.compiled = None        self.recompile()         btags = self.regexdisplay.bindtags()        self.regexdisplay.bindtags(btags[1:] + btags[:1])         btags = self.stringdisplay.bindtags()        self.stringdisplay.bindtags(btags[1:] + btags[:1])     def addoptions(self):        self.frames = []        self.boxes = []        self.vars = []        for name in ('IGNORECASE',                     'LOCALE',                     'MULTILINE',                     'DOTALL',                     'VERBOSE'):            if len(self.boxes) % 3 == 0:                frame = Frame(self.master)                frame.pack(fill=X)                self.frames.append(frame)            val = getattr(re, name)            var = IntVar()            box = Checkbutton(frame,                    variable=var, text=name,                    offvalue=0, onvalue=val,                    command=self.recompile)            box.pack(side=LEFT)            self.boxes.append(box)            self.vars.append(var)     def getflags(self):        flags = 0        for var in self.vars:            flags = flags | var.get()        flags = flags        return flags     def recompile(self, event=None):        try:            self.compiled = re.compile(self.regexdisplay.get(),                                       self.getflags())            bg = self.promptdisplay['background']            self.statusdisplay.config(text="", background=bg)        except re.error, msg:            self.compiled = None            self.statusdisplay.config(                    text="re.error: %s" % str(msg),                    background="red")        self.reevaluate()     def reevaluate(self, event=None):        try:            self.stringdisplay.tag_remove("hit", "1.0", END)        except TclError:            pass        try:            self.stringdisplay.tag_remove("hit0", "1.0", END)        except TclError:            pass        self.grouplist.delete(0, END)        if not self.compiled:            return        self.stringdisplay.tag_configure("hit", background="yellow")        self.stringdisplay.tag_configure("hit0", background="orange")        text = self.stringdisplay.get("1.0", END)        last = 0        nmatches = 0        while last <= len(text):            m = self.compiled.search(text, last)            if m is None:                break            first, last = m.span()            if last == first:                last = first+1                tag = "hit0"            else:                tag = "hit"            pfirst = "1.0 + %d chars" % first            plast = "1.0 + %d chars" % last            self.stringdisplay.tag_add(tag, pfirst, plast)            if nmatches == 0:                self.stringdisplay.yview_pickplace(pfirst)                groups = list(m.groups())                groups.insert(0, m.group())                for i in range(len(groups)):                    g = "%2d: %r" % (i, groups[i])                    self.grouplist.insert(END, g)            nmatches = nmatches + 1            if self.showvar.get() == "first":                break         if nmatches == 0:            self.statusdisplay.config(text="(no match)",                                      background="yellow")        else:            self.statusdisplay.config(text="")  # Main function, run when invoked as a stand-alone Python program. def main():    root = Tk()    demo = ReDemo(root)    root.protocol('WM_DELETE_WINDOW', root.quit)    root.mainloop() if __name__ == '__main__':    main()