how to read a file into array in python

text_file = open("filename.dat", "r")
lines = text_file.readlines()
print lines
print len(lines)
text_file.close()

def readFile(fileName):
        fileObj = open(fileName, "r") #opens the file in read mode
        words = fileObj.read().splitlines() #puts the file into an array
        fileObj.close()
        return words