Speed up code

[sfsinger19103]

See https://towardsdatascience.com/6-bad-manners-makes-your-python-program-slower-15b6fce62927

• Replace 'import ' with 'from import ' where reasonable. Importing a whole module when you're using only part of it can slow things down.
• Avoid dot-dot chaining
• Use for loop, not while loop, wherever possible