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  1. # list_intersection.py
  2. # MIT OCW 6.189 Homework 3
  3. # Exercise 3.1 – Additional List Practice
  4. # Mechanical MOOC
  5. # Written for Python 3
  6. # Glenn Richard
  7. # July 15, 2013
  8. def list_intersection(list_1, list_2):
  9.     # return intersection of list_1 and list_2
  10.     return [item for item in list_1 if item in list_2]
  11.  
  12. print("list_intersection")
  13. print(list_intersection([1, 3, 5], [5, 3, 1]))
  14. print(list_intersection([1, 3, 6, 9], [10, 14, 3, 72, 9]))
  15. print(list_intersection([2, 4, 6], [1, 3, 5]))
  16. # but a problem occurs when duplicates appear in a list ...
  17. print(list_intersection([1, 1, 2, 3, 5, 8, 13], [1, 3, 5, 7, 9, 11, 13]))
  18. print(list_intersection([1, 3, 5, 7, 9, 11, 13], [1, 1, 2, 3, 5, 8, 13]))
  19.  
  20. def list_intersection_unique(list_1, list_2):
  21.     # return intersection of list_1 and list_2 - essentially, set intersection
  22.     # so, each item that appears in both lists appears once in the returned new list
  23.     return list({item for item in list_1 if item in list_2})
  24. print("list_intersection_unique")
  25. print(list_intersection_unique([1, 1, 2, 3, 5, 8, 13], [1, 3, 5, 7, 9, 11, 13]))
  26.  
  27.  
  28. def list_intersection_minimalist(list_1, list_2):
  29.     # return a new list in which
  30.     # each item appears the lesser of the number of times
  31.     # that it appears either list
  32.     new_list = []
  33.     for item in set(list_1):
  34.         new_list += [item] * min(list_1.count(item), list_2.count(item))
  35.     return new_list
  36. print("list_intersection_minimalist")
  37. print(list_intersection_minimalist([1, 1, 1, 2, 3, 4], [1, 2, 1, 3, 7]))
  38. print(list_intersection_minimalist([1, 2, 1, 3, 7], [1, 1, 1, 2, 3, 4]))
  39.  
Success #stdin #stdout 0.05s 9568KB
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Standard input is empty
stdout
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list_intersection
[1, 3, 5]
[3, 9]
[]
[1, 1, 3, 5, 13]
[1, 3, 5, 13]
list_intersection_unique
[1, 3, 5, 13]
list_intersection_minimalist
[1, 1, 2, 3]
[1, 1, 2, 3]
https://ideone.com/pzRLZ5
MIT OCW 6.189 Homework 3 - Exercise 3.1 - Additional List Practice
language:
Python 3 (python  3.9.5)
created:
10 years ago
visibility:
public

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