What alternative is there to execfile in Python 3? / How to include a Python file?

It seems like in Python 3 they've removed all of the easy ways to quickly load a script, by removing execfile().

What alternative is there to include a Python file in another one, and execute it?

According to the Python documentation, instead of this:

execfile("./filename") 

Use this:

exec(open("./filename").read())

See Python's docs for:

• What’s New In Python 3.0
• execfile
• exec