The ITK Python Quick Start Guide has been updated for ITK 5.0! 
From basic examples, e.g.:
import itk
import sys
input_filename = sys.argv[1]
output_filename = sys.argv[2]
image = itk.imread(input_filename)
median = itk.median_image_filter(image, radius=2)
itk.imwrite(median, output_filename)
to quick descriptions on how to:
- Mix ITK and NumPy
- Understand ITK Python types
- Instantiate an ITK object
- Specify filter parameters
this is a helpful resource when getting started in Python.
Enjoy ITK!