Design a data structure to implement a phone book. Can search by name or number

Use Trie

class Trie:
    def __init__(self):
        self.root = {}

    def add(self, name, number):
        # Add name/number to the Trie
        node = self.root
        for char in name:
            if char not in node:
                node[char] = {}
            node = node[char]
        node["Number"] = number

    def find(self, prefix):
        # Return node after consuming given prefix
        node = self.root
        for char in prefix:
            if char not in node.keys():
                return None
            node = node[char]
        return node
# Then a hashtable for numbers as key, names as value
# Or let Trie has number as children