Best way I can think of is adding an invisible function field boolean on view. 

is_po = field.boolean(compute=_is_po)

@api.depends('field1') 
def _is_po_so(self):
    #your code
    self.is_po = False
========================
View
========================
<field name="is_po" invisible="1"/>
<button name="Button 1" attrs="{'invisible':[('is_po','=',True)]}" />
<button name="Button 1" attrs="{'invisible':[('is_po','=',False)]}" />

Check the above suedo code. 

Hope it helps.