A really light implementation of lazy load technique, yet powerful and conveniet.
Simply call this:
var1 = superlazy('key', default_value)
Your var1 will be loaded in load_setting(key) when accessed first time.
That's it. No subclassing is needed, no declaration is needed. Value type is auto detected and handled gracefully. str, int, list, dict can all be lazily loaded from anywhere you want now.
Python, 64 lines
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Copy to clipboard1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 | def load_setting(key):
# Just some dummy values for demo
if key == 'key':
return '123123'
elif key == 'limit':
return 123123
elif key == 'dummylist':
return [1, 2, 3, 4, 5]
elif key == 'crap':
return {'good': "boy"}
def superlazy(key, default):
class T(type(default)):
@staticmethod
def __loader__():
ret = load_setting(key)
if ret:
setattr(T, '__cache__', ret)
delattr(T, '__loader__')
def force(k, v):
def _wrapper(*args, **kwargs):
if hasattr(T, '__loader__'):
T.__loader__()
if hasattr(T, '__cache__'):
c = T.__cache__
func = getattr(c, k)
return func(*args[1:], **kwargs)
return v(*args, **kwargs)
return _wrapper
t = T(default)
for k, v in type(default).__dict__.iteritems():
if (k in ['__doc__']): continue
setattr(T, k, force(k, v))
return t
# Lazy string
a = superlazy("key", 'hahahaha')
print a, isinstance(a, str)
# Lazy int
b = superlazy("limit",9)
print 1 + b, isinstance(b, int)
print str(b)
# Lazy list
c = superlazy("dummylist", [1, 2, 3])
print c
print c[0]
print len(c)
# Lazy dict
d = superlazy("crap", {'a': 1, 'b': 2, 'c': 3})
print isinstance(d, dict)
print d
print d.get('a')
# Not existed lazy int, default value is used
e = superlazy("wer", 321)
print isinstance(e, int)
print e
|
Tags: lazy
setattr(T, '__cache__', ret)should be written asT.__cache__ = retdelattr(T, '__loader__')shoulc be written asdel T.__loader__