How to initialize a dict with keys from a list and empty value in Python?

by

dict.fromkeys directly solves the problem:

>>> dict.fromkeys([1, 2, 3, 4])
{1: None, 2: None, 3: None, 4: None}

This is actually a classmethod, so it works for dict-subclasses (like collections.defaultdict) as well.

The optional second argument, which defaults to None, specifies the value to use for the keys. Note that the same object will be used for each key, which can cause problems with mutable values:

>>> x = dict.fromkeys([1, 2, 3, 4], [])
>>> x[1].append('test')
>>> x
{1: ['test'], 2: ['test'], 3: ['test'], 4: ['test']}

More Related Contents:

  1. How can I remove a key from a Python dictionary?
  2. Reverse / invert a dictionary mapping
  3. Convert list of dictionaries to a pandas DataFrame
  4. How do I initialize a dictionary of empty lists in Python?
  5. How to return dictionary keys as a list in Python?
  6. How to delete items from a dictionary while iterating over it?
  7. Dictionary: Get list of values for list of keys
  8. In Python, when to use a Dictionary, List or Set?
  9. How to convert a dataframe to a dictionary
  10. Create a list with initial capacity in Python
  11. How do you create nested dict in Python?
  12. Inverting a dictionary with list values
  13. How to check if a map contains a key in Go?
  14. How to get the difference between two dictionaries in Python?
  15. Is there a clever way to pass the key to defaultdict’s default_factory?
  16. How to get rid of double backslash in python windows file path string? [duplicate]
  17. How do I sort a dictionary by key?
  18. python tuple to dict
  19. Appending a dictionary to a list in a loop
  20. One liner: creating a dictionary from list with indices as keys
  21. Can PyYAML dump dict items in non-alphabetical order?
  22. Object-like attribute access for nested dictionary
  23. How do I delete items from a dictionary while iterating over it?
  24. Counting each letter’s frequency in a string
  25. Checking a nested dictionary using a dot notation string “a.b.c.d.e”, automatically create missing levels
  26. How to create a Python dictionary with double quotes as default quote format?
  27. How to update the value of a key in a dictionary in Python?
  28. How to raise error if duplicates keys in dictionary
  29. How to make a list as the default value for a dictionary? [duplicate]
  30. TypedDict when keys have invalid names

Leave a Comment