""" Defines a class that represents a partition of a list of integers
:author: Michel Bierlaire
:date: Thu Oct 26 17:30:36 2023
"""
import logging
from typing import Iterable, Iterator, Optional
Segment = set[int]
logger = logging.getLogger(__name__)
[docs]
class Partition:
"""Class defining a partition of a set"""
[docs]
def __init__(self, segments: Iterable[Segment], full_set: Optional[Segment] = None):
self.segments = segments
if full_set:
self.full_set = full_set
else:
logger.warning(
'The full set of the partition has not been specified. It is defined '
'by default as the union of the provided segment.'
)
self.full_set = set().union(*self.segments)
self.validate_segments()
self.validate_partition()
[docs]
def number_of_segments(self):
return len(self.segments)
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def validate_segments(self):
"""Check the types"""
for segment in self.segments:
if not isinstance(segment, set):
raise ValueError('Each segment must be of type "set".')
if not segment:
raise ValueError('Partition contains empty segment')
for item in segment:
if not isinstance(item, int):
raise ValueError('Each item in the segment must be an integer.')
[docs]
def validate_partition(self):
"""Check that there is no intersection between segments"""
for s1, segment1 in enumerate(self.segments):
for s2, segment2 in enumerate(self.segments):
if s1 != s2:
intersection = segment1.intersection(segment2)
if intersection:
raise ValueError(
f'Elements in two different segments: {intersection}.'
)
# Check that the union of all segments is the given set
union_of_segments = set().union(*self.segments)
if union_of_segments != self.full_set:
missing_elements = self.full_set - union_of_segments
raise ValueError(
f'The union of segments does not match the given set. '
f'Missing elements: {missing_elements}.'
)
def __iter__(self) -> Iterator[Segment]:
return iter(self.segments)