[] and {} vs list() and dict(), which is better?

by

In terms of speed, it’s no competition for empty lists/dicts:

>>> from timeit import timeit
>>> timeit("[]")
0.040084982867934334
>>> timeit("list()")
0.17704233359267718
>>> timeit("{}")
0.033620194745424214
>>> timeit("dict()")
0.1821558326547077

and for non-empty:

>>> timeit("[1,2,3]")
0.24316302770330367
>>> timeit("list((1,2,3))")
0.44744206316727286
>>> timeit("list(foo)", setup="foo=(1,2,3)")
0.446036018543964
>>> timeit("{'a':1, 'b':2, 'c':3}")
0.20868602015059423
>>> timeit("dict(a=1, b=2, c=3)")
0.47635635255323905
>>> timeit("dict(bar)", setup="bar=[('a', 1), ('b', 2), ('c', 3)]")
0.9028228448029267

Also, using the bracket notation lets you use list and dictionary comprehensions, which may be reason enough.

More Related Contents:

  1. Python: get a dict from a list based on something inside the dict
  2. Python: iterating over list vs over dict items efficiency
  3. Access nested dictionary items via a list of keys?
  4. Why can’t I use a list as a dict key in python?
  5. How can I get list of values from dict?
  6. How do I merge a list of dicts into a single dict?
  7. Grouping Python dictionary keys as a list and create a new dictionary with this list as a value
  8. Getting a list of values from a list of dicts
  9. How do I initialize a dictionary of empty lists in Python?
  10. Replace values in list using Python [duplicate]
  11. Pandas DataFrame to List of Dictionaries
  12. Creating a list of dictionaries results in a list of copies of the same dictionary
  13. How can I make a dictionary from separate lists of keys and values?
  14. What is the time complexity of popping elements from list in Python?
  15. How to convert list of key-value tuples into dictionary?
  16. Python – How to check list monotonicity
  17. Merging dictionary value lists in python
  18. join two lists of dictionaries on a single key
  19. Python – sum values in dictionary
  20. Setting a value in a nested Python dictionary given a list of indices and value
  21. Creating an empty list in Python
  22. Dictionary vs Object – which is more efficient and why?
  23. Changing one dict changes all dicts in a list of dicts [duplicate]
  24. Appending to list in Python dictionary [duplicate]
  25. sum each value in a list of tuples
  26. Mapping dictionary value to list
  27. Which is the most efficient way to iterate through a list in python?
  28. How to sort a list of dictionaries by a value of the dictionary in Python?
  29. Length of longest word in a list
  30. How to create a nested dictionary from a list in Python?

Leave a Comment