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Python Python Collections (2016, retired 2019) Sets Set Math

Missing something about how sets work: print(fib.issubset(prime))

fib = {1,2,3,5,8,13,21,34,55,89,174}
prime = {1,2,3,5,7,9,13,17,19,22,29}

# from the python documentation
# ................................................................
#issubset(other)
#set <= other
#Test whether every element in the set is in other.

print(fib.issubset(prime))

#8 in fib, not in prime
#21 in fib, not in prime
#34, 55, 89, 174 in fib, not in prime

# yet, when I run it, returns True

The documentation seems straightforward, but clearly I am missing something.

2 Answers

Steven Parker
Steven Parker
229,744 Points

When I run it, I get False.

I tried it in the Treehouse workspace REPL, and also in my locally-installed Python (version 3.2.5).

Where are you trying it?

Hi Steve, I ran it local, copy and pasted, I'll look at it again. I know it should return false like you got... That time I got False. I swear I ran it 3 or 4 times looking at it each time, cause I was going to use it in some code, and it wasn't doing what I expected. Well thanks for looking.

Chris Komaroff
PLUS
Chris Komaroff
Courses Plus Student 14,198 Points

Thanks for heads up on .issubset(). Maybe a simpler example:

>>> a_set = {1,2,3,4,5}
>>> b_set = {3,4}
>>> a_set.issubset(b_set)
False
>>> b_set.issubset(a_set)
True
>>>