It seems like you are using windows so you need to download the get-pip.py and run like this.
Path_to_your_Python.exe\python.exe Path_to_get-pip.py\get-pip.py tweepy
Here is the link for download get-pip.py
It seems like you are using windows so you need to download the get-pip.py and run like this.
Path_to_your_Python.exe\python.exe Path_to_get-pip.py\get-pip.py tweepy
Here is the link for download get-pip.py