CODEWITHSUNDEEP
pythonfunctionbuilt-in
rhawker
rhawker

Reputation: 43

Python's all() not giving the expected result checking a list of small numbers are less than some value

In a python console (using 2.7) if I put in the following code:

vals = [1.2e-5, 1.5e-5, 3.2e-5, 4.5e-5]
for val in vals: print val < 0.001,

The output is True True True True as expected.

But! Here is my problem, if I try all(vals) < 0.001 it returns false?

Is it the number formatting giving it problems or something else? If I do this again but replace the vals list with vals = [2,2,2,2] and check for < 3 I get the desired output both ways!

EDIT Helpful answers, it is interesting to note that all([0.1, 0.1, 0.1]) evaluates to True, but 0.1 == True evaluates to False? What's up with this? Is it that a "nonzero" value will evaluate to True but is not actually "True"?

Upvotes: 2

Views: 57

Answers (2)

Amadan
Amadan

Reputation: 198486

Your usage is wrong. all(x < 0.001 for x in vals) should be okay.

all(vals) < 0.001 will check whether all vals is truthy, then compare the True or False you get as the result with 0.001, which is weird.

Upvotes: 2

BrenBarn
BrenBarn

Reputation: 251578

all(vals) checks whether all the values are boolean True (i.e., nonzero). That is True. True is not less than 0.001.

I think you want something like all(val < 0.001 for val in vals).

Upvotes: 2

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