How do you run a Python file with extension .py from Python 3.7.0b2?

Python 3.7.Ob2 is Python's Integrated Development and Learning Envrionment.

You can write your code directly in Python 3.7.0b2 or you can create a file with text editor and save it with extension .py and run it from Python 3.7.0b2.
For running a .py file, you must first create a file. Here is a file called helloworld.py and save it to your location of choice.
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pythonfile_1
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Now launch Python 3.7.0b2 and type in the following statement and enter to execute.
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Pythonfile_2
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Notice you need double slashes.