How to change button icon when button clicked, python quickly

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http://askubuntu.com – I'm trying to implement hide function in my application. What I want is to have this little arrow ">" when is hide and "V" when is visible. I know how to make it so its hides and shows but I need that little arrow to change whenever I click on it.... I'm using quickly and python to create my app. I tried set_icon_from_stock function but it returns error: AttributeError: 'ToolButton' object has no attribute 'set_icon_from_stock' Above example of arrow I talking about. Thanks (HowTos)