C:\>pip install tweepy
The first command is enough provided that pip has been added to the Path environment variable of your system. To check it out, do this:
- Open Command Prompt (DOS prompt).
- Type python and press enter.
- Once python prompt (>>>) appears, type import pip and press enter.
If you see an error, then pip has not been added to the environment variable Path. If there's no error whatsoever, then pip is installed properly.
In that case, re-install Python once and try again. I am using Python 3.5 and tweepy works fine for me. I see that you are using Python 2.7 version. I hope Python has been properly installed. If you want, try uninstalling Python and then re-installing it properly just to make sure. I will also suggest you to try using Python 3.x version once to see if you get the same error.
Hope it helps.