Checking the opening of an attribute table with pyqgis

I know how to show the attribute table of a specific layer (with showAttributeTable), but how to check if the attribute table of a specific layer is already opened ? I don't want to show it again if it's already visible.

Answer

You could use something like the following:

from PyQt4.QtGui import QApplication

attrTables = [d for d in QApplication.instance().allWidgets() if d.objectName() in (u'QgsAttributeTableDialog', u'AttributeTable')]
for x in attrTables:
    if 'layerName' in x.windowTitle():
        pass
    else:

        # do something

---

Edit:

As @Etienne mentioned in the comments, you could use the following for a more accurate method of obtaining the attribute table of a specific layer (assuming no layers have duplicate names):

from PyQt4.QtGui import QApplication

attrTables = [d for d in QApplication.instance().allWidgets() if d.objectName() in (u'QgsAttributeTableDialog', u'AttributeTable')]
for x in attrTables: 
    w_title = x.windowTitle() 

    tab_lyr = w_title[:w_title.index("::")-1]
    if tab_lyr == 'layer_name':
        # do something