def inner_join(lot0, lot1, key0=None, key1=None, sort=True):
''' Joins two lists of tuples (or namedtuples) on a key field.
If a keyfunc is not specified, it defaults to the first field in each tuple.
Returns a sorted list in the form: result [(key, lot1_tuple, lot2_tuple) ...]
Keys in lot0 but not lot1 raise a KeyError.
Keys in lot1 but not lot0 are silently ignored.
Tuples with a non-unique key (duplicates) are silently ignored.
Keys must be hashable and orderable or a TypeError is raised.
Running time is O(n log n) due to the sorting step.
from collections import namedtuple
Employee = namedtuple('Employee', 'name dept paygrade')
Person = namedtuple('Person', 'name age gender status')
ee = [Employee('adam', 'acct', 8),
... Employee('betty', 'sales', 9),
... Employee('charlie', 'acct', 2),
... ]
pp = [Person('adam', 30, 'm', 'single'),
... Person('betty', 28, 'f', 'married'),
... Person('charlie', 40, 'm', 'single'),
... ]
for k, e, p in inner_join(ee, pp):
... print k, e.dept, p.age
adam acct 30
betty sales 28
charlie acct 40
'''
key0 = key0 or (lambda r: r[0])
key1 = key1 or (lambda r: r[0])
d0 = {key0(r): r for r in lot0}
d1 = {key1(r): r for r in lot1}
seq = sorted(d0) if sort else iter(d0)
return [(k, d0[k], d1[k]) for k in seq]
if __name__ == '__main__':
import doctest
print doctest.testmod()
Diff to Previous Revision
--- revision 1 2011-11-01 18:49:01
+++ revision 2 2011-11-01 20:10:34
@@ -14,12 +14,12 @@
Employee = namedtuple('Employee', 'name dept paygrade')
Person = namedtuple('Person', 'name age gender status')
ee = [Employee('adam', 'acct', 8),
- ... Employee('betty', 'sales', 9),
- ... Employee('charlie', 'acct', 2),
+ ... Employee('betty', 'sales', 9),
+ ... Employee('charlie', 'acct', 2),
... ]
pp = [Person('adam', 30, 'm', 'single'),
- ... Person('betty', 28, 'f', 'married'),
- ... Person('charlie', 40, 'm', 'single'),
+ ... Person('betty', 28, 'f', 'married'),
+ ... Person('charlie', 40, 'm', 'single'),
... ]
for k, e, p in inner_join(ee, pp):
... print k, e.dept, p.age
