Hashing Table in Python

I just want your opinion about that code! :)

import random

class Error(Exception):
    def __init__(self, error=None):
        self.error = error

    def __str__(self):
        return str(self.error)

class HashTable(object):

    def __init__(self):
        self.length = 20
        self.keys = []
        self.table = [[] for _ in range(self.length)]

    def __len__(self):
        return self.length

    def __setitem__(self, key, value):
        self.keys.append(key)
        hashed_key = self._hash(key)
        self.table[hashed_key].append((value))  #Wartosc jest dodawana do listy pod hashowanym indeksem
    
    def _hash(self, key) :
        return hash(key) % self.length
    
    def show_list(self):
        return self.table
    
    def __getitem__(self, key):
        for el in self.table[self._hash(key)]:
            if el[0] == key:
                return el[1]
            
    def __delitem__(self, key):
        for el in self.table[self._hash(key)]:
            if el[0] == key:
                self.table[self._hash(key)].remove(el)
            
    def __iter__(self):
        def Generator(data):
            mylist = [_ for _ in data]
            for i in mylist:
                yield i
        return Generator(self.table)
                    
L = HashTable()
content = []
with open("song.txt", 'r', encoding = 'utf8') as travis:
    for line in travis:
        for word in line.split():
            content.append(word)

for c in content:
    L[c] = c
    
for x in L:
    print(x)

I've also will be really greateful for any tips and how to improve this one! :D