How do I import other Python files?

How do I import files in Python? I want to import:

1. a file (e.g. file.py)
2. a folder
3. a file dynamically at runtime, based on user input
4. one specific part of a file (e.g. a single function)

importlib was added to Python 3 to programmatically import a module.

import importlib

moduleName = input('Enter module name:')
importlib.import_module(moduleName)

The .py extension should be removed from moduleName. The function also defines a package argument for relative imports.

In python 2.x:

• Just import file without the .py extension
• A folder can be marked as a package, by adding an empty __init__.py file
• You can use the __import__ function, which takes the module name (without extension) as a string extension

pmName = input('Enter module name:')
pm = __import__(pmName)
print(dir(pm))

Type help(__import__) for more details.