...
OpenPerspective("org.python.pydev.ui.PythonPerspective");
...

public static void OpenPerspective(String idPerspective) {
		IPerspectiveDescriptor[] perspectives = PlatformUI.getWorkbench().getPerspectiveRegistry().getPerspectives();
		IPerspectiveDescriptor per = null;
		IWorkbenchPage page = getActivePage();

		for (IPerspectiveDescriptor descriptor : perspectives) {
			if (descriptor.getId().equals(idPerspective)) {
				per = descriptor;
			}
		}

		if (page != null) {
			page.setPerspective(per);
		} else {
		}
	}

	private static IWorkbenchPage getActivePage() {
		IWorkbenchPage result = null;
		IWorkbenchWindow window = PlatformUI.getWorkbench().getActiveWorkbenchWindow();
		if (window != null) {
			result = window.getActivePage();
		}
		return result;
	}