Use QListWidget.currentRow to get the index of the current item:
def print_info():
print myListWidget.currentRow()
print myListWidget.currentItem().text()
A QListWidgetItem does not know its own index: it's up to the list-widget to manage that.
You should also note that currentItemChanged sends the current and previous items as arguments, so you could simplify to:
def print_info(current, previous):
print myListWidget.currentRow()
print current.text()
print current.isSelected()
...