How can I identify when a Button is released in Tkinter?

You can create bindings for the <ButtonPress> and <ButtonRelease> events independently.

A good starting point for learning about events and bindings is here: http://effbot.org/tkinterbook/tkinter-events-and-bindings.htm

Here's a working example:

import Tkinter as tkimport timeclass Example(tk.Frame):    def __init__(self, *args, **kwargs):        tk.Frame.__init__(self, *args, **kwargs)        self.button = tk.Button(self, text="Press me!")        self.text = tk.Text(self, width=40, height=6)        self.vsb = tk.Scrollbar(self, command=self.text.yview)        self.text.configure(yscrollcommand=self.vsb.set)        self.button.pack(side="top")        self.vsb.pack(side="right", fill="y")        self.text.pack(side="bottom", fill="x")        self.button.bind("<ButtonPress>", self.on_press)        self.button.bind("<ButtonRelease>", self.on_release)    def on_press(self, event):        self.log("button was pressed")    def on_release(self, event):        self.log("button was released")    def log(self, message):        now = time.strftime("%I:%M:%S", time.localtime())        self.text.insert("end", now + " " + message.strip() + "\n")        self.text.see("end")if __name__ == "__main__":    root = tk.Tk()    Example(root).pack(side="top", fill="both", expand=True)    root.mainloop()