def read_file(file_name):
    open_file = open(file_name,'r')
    while True:
        file_line = open_file.readline()
        if not file_line:
            break
        yield file_line
    open_file.close()

# 调用read_file生成器。
a = read_file('/var/log/data/test.log')
for i in a:
    print (i)