from keras import backend as K
K.dtype(K.placeholder(shape=(2,4,5)))
'float32'
K.dtype(K.placeholder(shape=(2,4,5), dtype='float32'))
'float32'
K.dtype(K.placeholder(shape=(2,4,5), dtype='float64'))
'float64'
# Keras variable
kvar = K.variable(np.array([[1, 2], [3, 4]]))
K.dtype(kvar)
'float32'
kvar = K.variable(np.array([[1, 2], [3, 4]]), dtype='float32')
K.dtype(kvar)
'float32'