Running Python from Atom
The script package does exactly what you're looking for: https://atom.io/packages/script
The package's documentation also contains the key mappings, which you can easily customize.
Download and Install package here: https://atom.io/packages/script
To execute the python command in atom use the below shortcuts:
For Windows/Linux, it's SHIFT + Ctrl + B OR Ctrl + SHIFT + B
If you're on Mac, press ⌘ + I