'builtin_function_or_method' object has no attribute 'split'

edit

Code:

import matplotlib.pyplot as plt
%matplotlib inline
import numpy as np
file = 'IV meas -1.50E+0 V to 1.50E+0 V PHY 364 Practical_Dark_temp_25.57oC_Intensity_0.000suns -light OFF- 0 sec wait at 0 Volt.txt'
f=open(file,'r')
delimiter = ','

line=f.readline()
while (line != ''):
    data=line.split(delimiter)
    V1L.append(float(data[0]))
    I1L.append(float(data[1]))
    line=f.readline

each line in the txt file is of the form

-1.50000E+0,-3.22013E-3