How to set default value to all keys of a dict object in python?

Question

I know you can use setdefault(key, value) to set default value for a given key, but is there a way to set default values of all keys to some value after creating a dict ?

Answer 1

Use defaultdict

from collections import defaultdict
a = {} 
a = defaultdict(lambda:0,a)
a["anything"] # => 0

This is very useful for case like this,where default values for every key is set as 0:

results ={ 'pre-access' : {'count': 4, 'pass_count': 2},'no-access' : {'count': 55, 'pass_count': 19}
for k,v in results.iteritems():
  a['count'] += v['count']
  a['pass_count'] += v['pass_count']