How to transform the string of a QLineEdit into float?

Good evening everyone! I've been trying to transform the string of a Qline edit into float and I can not !! It always returns the error saying that I can not convert string to float. What can I do to get around this? I'm trying like this:

if float(self.qg_nodalloads[str(i)+str(0)].text())  > 0: 
   x =1