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"""http://ginstrom.com/scribbles/2007/10/08/design-patterns-python-style/
An example of the Template pattern in Python"""
ingredients = "spam eggs apple"
line = '-' * 10
# Skeletons
def iter_elements(getter, action):
"""Template skeleton that iterates items"""
for element in getter():
action(element)
print(line)
def rev_elements(getter, action):
"""Template skeleton that iterates items in reverse order"""
for element in getter()[::-1]:
action(element)
print(line)
# Getters
def get_list():
return ingredients.split()
def get_lists():
return [list(x) for x in ingredients.split()]
# Actions
def print_item(item):
print(item)
def reverse_item(item):
print(item[::-1])
# Makes templates
def make_template(skeleton, getter, action):
"""Instantiate a template method with getter and action"""
def template():
skeleton(getter, action)
return template
# Create our template functions
templates = [make_template(s, g, a)
for g in (get_list, get_lists)
for a in (print_item, reverse_item)
for s in (iter_elements, rev_elements)]
# Execute them
for template in templates:
template()
### OUTPUT ###
# spam
# ----------
# eggs
# ----------
# apple
# ----------
# apple
# ----------
# eggs
# ----------
# spam
# ----------
# maps
# ----------
# sgge
# ----------
# elppa
# ----------
# elppa
# ----------
# sgge
# ----------
# maps
# ----------
# ['s', 'p', 'a', 'm']
# ----------
# ['e', 'g', 'g', 's']
# ----------
# ['a', 'p', 'p', 'l', 'e']
# ----------
# ['a', 'p', 'p', 'l', 'e']
# ----------
# ['e', 'g', 'g', 's']
# ----------
# ['s', 'p', 'a', 'm']
# ----------
# ['m', 'a', 'p', 's']
# ----------
# ['s', 'g', 'g', 'e']
# ----------
# ['e', 'l', 'p', 'p', 'a']
# ----------
# ['e', 'l', 'p', 'p', 'a']
# ----------
# ['s', 'g', 'g', 'e']
# ----------
# ['m', 'a', 'p', 's']
# ----------