# -- use cases: --
def usecases():
from pprint import pprint
print '\n--- Sorting Simple Lists ---\n'
data = ['Jim', 'Will', 'Tom']
print data
data.sort( By(len) )
print data
print '\n--- Sorting Simple Tables ---\n'
data = [
('Jim', 21),
('Will', 24),
('Tom', 20),
]
pprint(data)
data.sort( ByColumn(0) ) # using straight forward comparator closure
pprint(data)
data.sort( By(Column(1)) ) # comparator/accessor closure combination
pprint(data)
print '\n--- Sorting Object Tables ---\n'
class Record:
def __init__(self, **kw): self.__dict__.update(kw)
def __repr__(self): return '<record %r>' % self.__dict__
data = [
Record(name='Jim', age=21),
Record(name='Will', age=24),
Record(name='Tom', age=20),
]
pprint(data)
data.sort( ByAttribute('name') ) # using straight forward comparator closure
pprint(data)
data.sort( By(Attribute('age')) ) # comparator/accessor closure combination
pprint(data)
# -- a straight forward approach: --
def ByColumn(key):
def compare(obj1, obj2): return cmp(obj1[key], obj2[key])
return compare
def ByAttribute(name):
def compare(obj1, obj2): return cmp(getattr(obj1, name), getattr(obj2, name))
return compare
# -- a somewhat more generic approach: --
def By(accessor):
def compare(left, right): return cmp( accessor(left), accessor(right) )
return compare
def Attribute(name):
def get(obj): return getattr(obj, name)
return get
def Column(key):
def get(obj): return obj[key]
return get
# -- demo: --
if __name__ == '__main__':
usecases()
