Welcome to the Treehouse Community

Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community! While you're at it, check out some resources Treehouse students have shared here.

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.

Start your free trial

Python

Posted by Gabriel Guerra
.a{fill-rule:evenodd;}techdegree seal-36
Gabriel Guerra
Data Analysis Techdegree Graduate 9,109 Points

TypeError: unsupported operand type(s) for &: 'set' and 'list'

HI there Any idea why I get this type error:

turkey = {'turkey', 'cheese'}
vegetarian = {'tomato', 'onion', 'mushrooms'}
denver = {'tomato', 'eggs'}
bacon = ['mushrooms', 'eggs']

shared_ingredients = vegetarian & bacon & denver
print(shared_ingredients)

Thanks, Gabriel

1 Answer

Jeff Muday
MOD
Jeff Muday
Treehouse Moderator 28,716 Points
Jeff Muday
Jeff Muday
Treehouse Moderator 28,716 Points

Python is more strict when it comes to sets and operators. These have to be all sets in order to be syntactically correct.

Perhaps you meant this:

turkey = {'turkey', 'cheese'}
vegetarian = {'tomato', 'onion', 'mushrooms'}
denver = {'tomato', 'eggs'}
bacon = {'mushrooms', 'eggs'} # here as a set { }

shared_ingredients = vegetarian & bacon & denver
print(shared_ingredients)

This is also correct:

turkey = {'turkey', 'cheese'}
vegetarian = {'tomato', 'onion', 'mushrooms'}
denver = {'tomato', 'eggs'}
bacon = set( ['mushrooms', 'eggs'] ) # converts the list to a set

shared_ingredients = vegetarian & bacon & denver
print(shared_ingredients)

This will result in the null set because there isn't an intersection of vegetarian, bacon, and denver.