Ruby hash quirks - part 3

ruby_hash_3.rb

[1] (pry) main: 0> my_hash = Hash.new { |hash, key| hash[key] = [] }
=> {}
[2] (pry) main: 0> my_hash[:hobbies] << 'swimming';
[3] (pry) main: 0> my_hash[:skills]  << 'java';
[4] (pry) main: 0> my_hash[:hobbies]
=> ["swimming"]
[5] (pry) main: 0> my_hash[:hobbies].object_id
=> 70144893987080
[6] (pry) main: 0> my_hash[:skills]
=> ["java"]
[7] (pry) main: 0> my_hash[:skills].object_id
=> 70144900036380
[8] (pry) main: 0> my_hash[:some_random_key]
=> []
[9] (pry) main: 0> my_hash[:some_random_key].object_id
=> 70144899955360