def func_onchange(metric):
def _inner_onchange(func):
"A decorator that runs a function only when a generic metric changes."
def decorated(*args, **kwargs):
try:
mresult = metric(*args, **kwargs)
if decorated._last_metric != mresult:
decorated._last_metric = mresult
decorated._last_result = func(*args, **kwargs)
except AttributeError:
decorated._last_metric = mresult
decorated._last_result = func(*args, **kwargs)
return decorated._last_result
return decorated
return _inner_onchange
def method_onchange(metric):
def _inner_onchange(method):
"A decorator that runs a method only when a generic metric changes."
met_name = "_%s_last_metric" % id(method)
res_name = "_%s_last_result" % id(method)
def decorated(self, *args, **kwargs):
try:
mresult = metric(*args, **kwargs)
if getattr(decorated, met_name) != mresult:
setattr(decorated, met_name, mresult)
setattr(decorated, res_name, method(self, *args, **kwargs))
except AttributeError:
setattr(decorated, met_name, mresult)
setattr(decorated, res_name, method(self, *args, **kwargs))
return getattr(decorated, res_name)
return decorated
return _inner_onchange
# simple check to see if file changed
def cheezy_file_metric(filename):
import os
return os.stat(filename)
# Function example, will only read file contents when file stats change
@func_onchange(cheezy_file_metric)
def get_filecontents(filename):
print 'reading "%s" contents' % filename
return file(filename).read()
file('test.txt', 'w').write('original content')
print '-'*60
print get_filecontents('test.txt')
print '-'*60
print get_filecontents('test.txt')
file('test.txt', 'w').write('new and improved content!')
print '-'*60
print get_filecontents('test.txt')
print '-'*60
print get_filecontents('test.txt')
print '~'*60
# Method example, will only read file contents when file stats change
class FileReadThing:
@method_onchange(cheezy_file_metric)
def get_filecontents(self, filename):
print 'reading "%s" contents' % filename
return file(filename).read()
f = FileReadThing()
file('test.txt', 'w').write('original content')
print '-'*60
print f.get_filecontents('test.txt')
print '-'*60
print f.get_filecontents('test.txt')
file('test.txt', 'w').write('new and improved content!')
print '-'*60
print f.get_filecontents('test.txt')
print '-'*60
print f.get_filecontents('test.txt')
