我是python脚本的新手，我正在使用python 2.7版本，我有.txt格式的数据，如下所示
DTMTYEAR LAT. 67.5 68.5 69.5 70.5 71.5 72.5 73.5 74.5 75.5 76.5 77.5
01011951 7.5 99.90 99.90 99.90 99.90 99.90 99.90 99.90 99.90 99.90 99.90 99.90
01011951 8.5 99.90 99.90 99.90 99.90 99.90 99.90 31.45 99.90 99.90 30.02 31.19
01011951 9.5 99.90 99.90 99.90 99.90 99.90 99.90 99.90 99.90 99.90 30.18 29.93
01011951 10.5 99.90 99.90 99.90 99.90 99.90 99.90 99.90 99.90 29.08 27.62 27.91
01011951 11.5 99.90 99.90 99.90 99.90 99.90 30.11 99.90 99.90 28.32 27.28 28.28
我希望这些数据采用xlsx格式，如下所示
x y value
7.5 67.5 99.90
7.5 68.5 99.90
7.5 69.5 99.90
7.5 70.5 99.90
7.5 71.5 99.90
7.5 72.5 99.90
7.5 73.5 99.90
7.5 74.5 99.90
7.5 75.5 99.90
7.5 76.5 99.90
7.5 77.5 99.90
8.5 67.5 99.90
8.5 68.5 99.90
依旧......
请帮我怎么做。