Exercises in Programming Style

Chapter 24

Quarantine

24.1 Constraints

• Core program functions have no side effects of any kind, including IO.
• All IO actions must be contained in computation sequences that are clearly separated from the pure functions.
• All sequences that have IO must be called from the main program.

24.2 A Program in this Style

  1 #!/usr/bin/env python
  2 import sys, re, operator, string
  3
  4 #
  5 # The Quarantine class for this example
  6 #
  7 class TFQuarantine:
  8 def __init__(self, func):
  9  self._funcs = [func]
 10
 11 def bind(self, func):
 12  self._funcs.append(func)
 13  return self
 14
 15 def execute(self):
 16  def guard_callable(v):
 17    return v() if hasattr(v, ...