What you have on your hands is an IPython Notebook file. (Now renamed to Jupyter Notebook
you can open it using the command ipython notebook filename.ipynb
from the directory it is downloaded on to.
If you are on a newer machine, open the file as jupyter notebook filename.ipynb
.
do not forget to remove the .txt extension.
the file has a series of python code/statements and markdown text that you can run/inspect/save/share. read more about ipython notebook from the website.
if you do not have IPython installed, you can do
pip install ipython
or check out installation instructions at the ipython website