PySide2 : setAttributeArray of QOpenGLShaderProgram does not have effect

values=(
       1,-1,
       1,-1,
      -1,1,
       1,1)
np_values = np.array(values)
stride  = 2

#This has no effect
self.program.setAttributeArray(0, GL_FLOAT, np_values, len(values), stride)   

self.program.setUniformValue( "t", self.t )

glf.glViewport(0, 0, self.viewportSize.width(), self.viewportSize.height());

glf.glDisable(GL_DEPTH_TEST)                
glf.glClearColor( 0.0, 0.0, 0.0, 1.0 )
glf.glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);
glf.glEnable(GL_BLEND)
glf.glBlendFunc(GL_SRC_ALPHA, GL_ONE)

# Because setAttributeArray fails to set values, this fails. 
glf.glDrawArrays(GL_TRIANGLE_STRIP, 0, 4 )