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Giorgio Sky
Courses Plus Student 115 PointsHow does comprehension work with range?
{round(x/y) for y in range(1,11) for x in range(2,21)}
Given the above code, what is going on? I would expect that every number in:
[2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20]
gets divided by every number in:
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
But the result is:
{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20}
How is this obtained? What does python do under the hoods? Thanks for any answer. And thanks for all these python courses, they are so useful. Really.
1 Answer
Iain Simmons
Treehouse Moderator 32,305 PointsBecause you're using the curly braces in this comprehension, you're doing a set comprehension, not a list comprehension. So you're getting the unique values, not all of them in order.
Change your curly braces to square brackets and you're all good to go:
>>> [round(x/y) for y in range(1,11) for x in range(2,21)]
[2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 1, 2, 2, 2, 3, 4, 4, 4, 5, 6, 6, 6, 7, 8, 8, 8, 9, 10, 10, 1, 1, 1, 2, 2, 2, 3, 3, 3, 4, 4, 4, 5, 5, 5, 6, 6, 6, 7, 0, 1, 1, 1, 2, 2, 2, 2, 2, 3, 3, 3, 4, 4, 4, 4, 4, 5, 5, 0, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 4, 4, 4, 0, 0, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 0, 0, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 3, 3, 3, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2]
Giorgio Sky
Courses Plus Student 115 PointsGiorgio Sky
Courses Plus Student 115 PointsYep, true, I missed that part of the explanation. Though they should be unordered, according to set documentation... am I wrong?
Thank you so much for the answer anyway ;)
Iain Simmons
Treehouse Moderator 32,305 PointsIain Simmons
Treehouse Moderator 32,305 PointsYou're not wrong: technically if it recorded the order it was inserted, 2 would be first. There may be some Python thing that just displays it in ascending order when every value is an integer.