defaultdict of defaultdict?

by

Yes like this:

defaultdict(lambda: defaultdict(int))

The argument of a defaultdict (in this case is lambda: defaultdict(int)) will be called when you try to access a key that doesn’t exist. The return value of it will be set as the new value of this key, which means in our case the value of d[Key_doesnt_exist] will be defaultdict(int).

If you try to access a key from this last defaultdict i.e. d[Key_doesnt_exist][Key_doesnt_exist] it will return 0, which is the return value of the argument of the last defaultdict i.e. int().

More Related Contents:

  1. Cost of len() function
  2. Is there a short contains function for lists?
  3. How can I create a Set of Sets in Python?
  4. How can this function be rewritten to implement OrderedDict? [duplicate]
  5. What is the purpose of collections.ChainMap?
  6. Subtracting two lists in Python
  7. Accessing items in an collections.OrderedDict by index
  8. Key-ordered dict in Python
  9. Why is Collections.counter so slow?
  10. Python defaultdict and lambda
  11. How to sort Counter by value? – python
  12. How to check if a tuple contains an element in Python?
  13. What’s the difference between the square bracket and dot notations in Python?
  14. Python if statements [closed]
  15. In Django, how does one filter a QuerySet with dynamic field lookups?
  16. How to avoid explicit ‘self’ in Python?
  17. Getting a machine’s external IP address with Python
  18. xls to csv converter
  19. Replace first occurrence only of a string?
  20. Compile Python code to statically linked executable with Cython
  21. How does the logical `and` operator work with integers? [duplicate]
  22. ImportError: Failed to import the Cloud Firestore library for Python
  23. How to strip all whitespace from string
  24. How can I replicate rows of a Pandas DataFrame?
  25. plotting a histogram on a Log scale with Matplotlib
  26. python subclass access to class variable of parent
  27. How to unpack a Series of tuples in Pandas?
  28. Cannot find the file specified when using subprocess.call(‘dir’, shell=True) in Python
  29. What is the effect of using `python -m pip` instead of just `pip`? [duplicate]
  30. How to get the Tkinter Label text?

Leave a Comment