This question originally asked (wrongly) what does "|" mean in Python, when the actual question was about Django. That question had a wonderful answer by Triptych I want to preserve.
In Python, the '|' operator is defined by default on integer types and set types.
If the two operands are integers, then it will perform a bitwise or, which is a mathematical operation.
If the two operands are set types, the '|' operator will return the union of two sets.
a = set([1,2,3])
b = set([2,3,4])
c = a|b # = set([1,2,3,4])
Additionally, authors may define operator behavior for custom types, so if something.property is a user-defined object, you should check that class definition for an __or__() method, which will then define the behavior in your code sample.
So, it's impossible to give you a precise answer without knowing the data types for the two operands, but usually it will be a bitwise or.