I have a defaultdict that looks like this:
dict1 = defaultdict(lambda: defaultdict(int))
The problem is, I can't pickle it using cPickle. One of the solution that I found here is to use module-level function instead of a lambda. My question is, what is module-level function? How can I use the dictionary with cPickle?
In addition to Martijn's explanation:
A module-level function is a function which is defined at module level, that means it is not an instance method of a class, it's not nested within another function, and it is a "real" function with a name, not a lambda function.
So, to pickle your defaultdict
, create it with module-level function instead of a lambda function:
def dd():
return defaultdict(int)
dict1 = defaultdict(dd) # dd is a module-level function
than you can pickle it
tmp = pickle.dumps(dict1) # no exception
new = pickle.loads(tmp)