Let's have a method that would cache results it calculates.
"If" approach:
def calculate1(input_values):
if input_values not in calculate1.cache.keys():
# do some calculation
result = input_values
calculate1.cache[input_values] = result
return calculate1.cache[input_values]
calculate1.cache = {}
"Except" approach:
def calculate2(input_values):
try:
return calculate2.cache[input_values]
except AttributeError:
calculate2.cache = {}
except KeyError:
pass
# do some calculation
result = input_values
calculate2.cache[input_values] = result
return result
"get/has" approach:
def calculate3(input_values):
if not hasattr(calculate3, cache):
calculate3.cache = {}
result = calculate3.cache.get(input_values)
if not result:
# do some calculation
result = input_values
calculate3.cache[input_values] = result
return result
Is there another (faster) way? Which one is most pythonic? Which one would you use?
Note: There's a speed difference:
calculate = calculateX # depening on test run
for i in xrange(10000):
calculate(datetime.utcnow())
Results time python test.py
:
calculate1: 0m9.579s
calculate2: 0m0.130s
calculate3: 0m0.095s
Use a collections.defaultdict. It's designed precisely for this purpose.