Exercises in Programming Style

Chapter 27

Lazy Rivers

27.1 Constraints

• Data is available in streams, rather than as a complete whole.
• Functions are filters/transformers from one kind of data stream to another.
• Data is processed from upstream on a need basis from downstream.

27.2 A Program in this Style

  1 #!/usr/bin/env python
  2 import sys, operator, string
  3
  4 def characters(filename):
  5 for line in open(filename):
  6  for c in line:
  7    yield c
  8
  9 def all_words(filename):
 10 start_char = True
 11 for c in characters(filename):
 12  if start_char == True:
 13    word = ""
 14    if c.isalnum():
 15    # We found the start of a word
 16    word = c.lower()
 17    start_char = False
 18    else: pass ...