Finding partial subsets python

Question

I'm looking for a way to get the number of elements of one set that appear in another set.

Given these two sets:

a = 'a b c d'
b = 'a b c e f'
a = set(a.split())
b = set(b.split())

This prints false:

print a.issubset(b) # prints False

Is there a pythonic way to instead print "3" since three elements of a appear in b?

DSM · Accepted Answer · 2015-11-17 22:19:18Z

10

IIUC, you can use set.intersection:

>>> a.issubset(b)
False
>>> a.intersection(b)
{'a', 'c', 'b'}
>>> len(a.intersection(b))
3

which could be abbreviated & since both a and b are sets:

>>> len(a & b)
3

answered Nov 17, 2015 at 22:19

DSM

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Comments

user764357 · Accepted Answer · 2015-11-17 22:20:22Z

1

You can you & and | to perform simple set algebra on python sets.

For example:

> a & b
set(['a', 'c', 'b'])
> a | b
set(['a', 'c', 'b', 'e', 'd', 'f'])

answered Nov 17, 2015 at 22:20

user764357