Remove banned pairs

Sometimes you may wish to ban certain pairs of players from a matching. This can be done by removing them from the game all together.

Consider the following preferences from an instance of HR.

resident_prefs = {
    "A": ["C"],
    "S": ["C", "M"],
    "D": ["C", "M", "G"],
    "J": ["C", "G", "M"],
    "L": ["M", "C", "G"],
}

hospital_prefs = {
    "M": ["D", "L", "S", "J"],
    "C": ["D", "A", "S", "L", "J"],
    "G": ["D", "J", "L"],
}

The pairs to be removed can be described as a list of hospital-resident tuples. This list needs to be iterated, and the preferences updated.

banned_pairs = [("M", "L"), ("C", "J")]
for hospital, resident in banned_pairs:
    hprefs = hospital_prefs[hospital]
    rprefs = resident_prefs[resident]

    if resident in hprefs:
        hprefs.remove(resident)
        hospital_prefs[hospital] = hprefs
    if hospital in rprefs:
        rprefs.remove(hospital)
        resident_prefs[resident] = rprefs

resident_prefs, hospital_prefs

({'A': ['C'],
  'S': ['C', 'M'],
  'D': ['C', 'M', 'G'],
  'J': ['G', 'M'],
  'L': ['C', 'G']},
 {'M': ['D', 'S', 'J'], 'C': ['D', 'A', 'S', 'L'], 'G': ['D', 'J', 'L']})