Vertical bar in Python bitwise assignment operator

Question

There is a code and in class\' method there is a line:

object.attribute |= variable

I can\'t understand what it means. I didn\'t find (|=)

Answer 1

I should add that "bar-equals" is now (in 2018) most popularly used as a set-union operator to append elements to a set if they're not there yet.

>>> a = {'a', 'b'}
>>> a
set(['a', 'b'])

>>> b = {'b', 'c'}
>>> b
set(['c', 'b'])

>>> a |= b
>>> a
set(['a', 'c', 'b'])

One use-case for this, say, in natural language processing, is to extract the combined alphabet of several languages:

alphabet |= {unigram for unigram in texts['en']}
alphabet |= {unigram for unigram in texts['de']}
...