How to limit the size of a comprehension?

by

You can use a generator expression to do the filtering, then use islice() to limit the number of iterations:

from itertools import islice

filtered = (i for i in a if i == 1)
b = list(islice(filtered, 3))

This ensures you don’t do more work than you have to to produce those 3 elements.

Note that there is no point anymore in using a list comprehension here; a list comprehension can’t be broken out of, you are locked into iterating to the end.

More Related Contents:

  1. Find a unique element in a list [closed]
  2. What does “list comprehension” and similar mean? How does it work and how can I use it?
  3. Flattening a shallow list in Python [duplicate]
  4. Is it Pythonic to use list comprehensions for just side effects?
  5. List comprehension without [ ] in Python
  6. Generator expressions vs. list comprehensions
  7. Are list-comprehensions and functional functions faster than “for loops”?
  8. List comprehension on a nested list?
  9. Create list of single item repeated N times
  10. How do I create a list of lambdas (in a list comprehension/for loop)?
  11. Transpose a matrix in Python [duplicate]
  12. Why is a list comprehension so much faster than appending to a list?
  13. List comprehension vs generator expression’s weird timeit results?
  14. Comprehension for flattening a sequence of sequences? [duplicate]
  15. Advanced Nested List Comprehension Syntax
  16. Weird behavior: Lambda inside list comprehension [duplicate]
  17. `elif` in list comprehension conditionals
  18. Python using enumerate inside list comprehension
  19. Why list comprehension is much faster than numpy for multiplying arrays?
  20. How to set local variable in list comprehension?
  21. How to read aloud Python List Comprehensions?
  22. Flattening a list of NumPy arrays?
  23. flatten list of list through list comprehension
  24. Converting List Comprehensions to For Loops in Python
  25. List comprehension scope error from Python debugger
  26. range(len(list)) or enumerate(list)? [duplicate]
  27. Creating a Python list comprehension with an if and break
  28. Square braces not required in list comprehensions when used in a function
  29. How to parallelize list-comprehension calculations in Python?
  30. How does all() in python work on empty lists

Leave a Comment