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I have a 3D coordinate tuple (x, y, z). I want to test that none of the 3 co-ords of a given tuple are below (a, b, c) and none are higher than (d, e, f). Through trial, error, and reading these forums I've learned that:

(a, b, c) <= (x, y, z) <= (d, e, f)

doesn't work as the first expression evaluates, then gets that outcome (0 or 1) and uses it in the next evaluation, and so on. So now I tried:

((a, b, c) <= (x, y, z)) and ((x, y, z) <= (d, e, f))

This doesn't work either because when it hits a True in any of the three paired comparisons (a, x; b, y; c, z; etc), it results in True. As such, tuple comparisons work more like decimal values rather than three separate scalar variables. I need any failure of all three pair-comparisons (six in total) to produce a False result rather than any success to produce a True.

I hoped for a method as sweetly simple as a <= b <= c. What is a simple method of doing this with tuples that only produces True when all pair-wise comparisons pass?

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3 Answers 3

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Assuming your lower and upper bound as well as your point are three-tuples, try this:

lower = 1,2,3
upper = 5,2,7
xyz = 2,3,4

all(u <= j <= v for u, j, v in zip(lower, xyz, upper))

Or just compare them individually:

(a <= x <= d) and (b <= y <= e) and (c <= z <= f)
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I want to say both you and falsetru gave the best answers. After mulling over falsetru's response, I was coming to the pythonic method that you came up with, Tobias. Thanks to you both!
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According to Expression - Comparison:

Tuples and lists are compared lexicographically using comparison of corresponding elements. ...

Define your own comparison function.

>>> def lte(x, y):
...     return all(a <= b for a, b in zip(x, y))
... 
>>> lte((1,2,3), (2,3,4))
True
>>> lte((1,2,3), (0,3,4))
False
>>> lte((1,2,3), (2,3,4)) and lte((2,3,4), (3,4,5))
True
>>> lte((1,2,3), (2,3,4)) and lte((2,3,4), (3,2,5))
False
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1

Through trial, error, and reading these forums I've learned that [...] doesn't work...

Except that it does, since Python chains relational operators.

>>> 3 < 4 < 5
True
>>> 5 > 4 > 3
True

This doesn't work either because when it hits a True in any of the three paired comparisons [...], it results in True.

Except that Python compares all elements in both sequence operands (of the same type).

>>> (1, 2, 3) >= (1, 2, 4)
False

Please verify that you are in fact using Python, since both of your observations are false in it.

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3 Comments

When I do print (35, 43, 29) <= (40 , 40, 40), I get True. The answer I want my testing to give me is False, as the 43 is not less than or equal to 40. Do you get something different, or do I have my less thans and greater thans mixed up again? :)
Then you need to specify that in the question.
If a<x, (a,b,c)<=(x,y,z) never checks the remaining values, as falsetru noted. OP did specify: when all pair-wise comparisons pass.

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