python技巧分享（八）

這是一個系列文章，主要分享python的使用建議和技巧，每次分享3點，希望你能有所收穫。

1 pip安裝指定版本號的包

root@master:demo$ pip install redis==2.7.4
OK
CLOSED
Collecting redis==2.7.4
Installing collected packages: redis
Successfully installed redis-2.7.4
root@master:demo$ pip uninstall redis
OK
CLOSED
Uninstalling redis-2.7.4:
  /opt/python-2.7.10/lib/python2.7/site-packages/redis-2.7.4.dist-info/DESCRIPTION.rst
  /opt/python-2.7.10/lib/python2.7/site-packages/redis-2.7.4.dist-info/INSTALLER
  /opt/python-2.7.10/lib/python2.7/site-packages/redis-2.7.4.dist-info/METADATA
  /opt/python-2.7.10/lib/python2.7/site-packages/redis-2.7.4.dist-info/RECORD
  /opt/python-2.7.10/lib/python2.7/site-packages/redis-2.7.4.dist-info/WHEEL
  /opt/python-2.7.10/lib/python2.7/site-packages/redis-2.7.4.dist-info/metadata.json
  /opt/python-2.7.10/lib/python2.7/site-packages/redis-2.7.4.dist-info/top_level.txt
  /opt/python-2.7.10/lib/python2.7/site-packages/redis/__init__.py
  /opt/python-2.7.10/lib/python2.7/site-packages/redis/__init__.pyc
  /opt/python-2.7.10/lib/python2.7/site-packages/redis/_compat.py
  /opt/python-2.7.10/lib/python2.7/site-packages/redis/_compat.pyc
  /opt/python-2.7.10/lib/python2.7/site-packages/redis/client.py
  /opt/python-2.7.10/lib/python2.7/site-packages/redis/client.pyc
  /opt/python-2.7.10/lib/python2.7/site-packages/redis/connection.py
  /opt/python-2.7.10/lib/python2.7/site-packages/redis/connection.pyc
  /opt/python-2.7.10/lib/python2.7/site-packages/redis/exceptions.py
  /opt/python-2.7.10/lib/python2.7/site-packages/redis/exceptions.pyc
  /opt/python-2.7.10/lib/python2.7/site-packages/redis/utils.py
  /opt/python-2.7.10/lib/python2.7/site-packages/redis/utils.pyc
Proceed (y/n)? y
  Successfully uninstalled redis-2.7.4
root@master:demo$ pip install redis==2.7.6
OK
CLOSED
Collecting redis==2.7.6
Installing collected packages: redis
Successfully installed redis-2.7.6

未安裝redis包時，運行pip install redis -v命令，可以看到所有可用版本的redis包，這裏先安裝redis-2.7.4，卸載後，再安裝redis-2.7.6。

2 以腳本形式運行python模塊

root@master:demo$ python -m timeit -s 'import time' -n 1 'time.sleep(0.88)'
1 loops, best of 3: 881 msec per loop

通過python的-m選項，將timeit模塊以腳本方式直接運行。這段代碼意思是計算time.sleep(0.88)的運行時間，由輸出可以看到，運行時間爲881毫秒。

3 python快速啓動一個web服務器

root@master:conf$ python -m SimpleHTTPServer 8080
Serving HTTP on 0.0.0.0 port 8080 ...

在本機瀏覽器中輸入http://localhost:8080/，會看到命令啓動路徑下的所有文件及目錄，單擊文件可以直接下載，很適合用於將目錄分享出去，供其他人訪問。