python 读取大文件，按照字节读取

def read_bigFile():
    f = open("123.dat",'r')
    cont = f.read()
    while len(cont) > :
        print(cont)
        cont = f.read()
　　f.close()
read_bigFile()

def copyFile():
    f1 = "123.dat"
    f2 = "123.dat.bak"
    #大文件复制
    fs1 = open(f1,'r')
    fs2 = open(f2,'w')
    cont1 = fs1.readline()

    while len(cont1)>:
        #写入
        fs2.write(cont1)
        cont1 = fs1.readline()
    fs1.close()
    fs2.close()
copyFile()