call by reference (ruby / python)

name_ref.py

some_guy = 'Fred'

first_names = []
first_names.append(some_guy)

another_list_of_names = first_names
another_list_of_names.append('George')

some_guy = 'Bill'

print (some_guy, first_names, another_list_of_names)

name_ref.rb

some_guy = 'Fred'

first_names = []
first_names.push(some_guy)

another_list_of_names = first_names
another_list_of_names.push('George')

some_guy = 'Bill'

another_list_of_names[0] = some_guy

print some_guy, first_names, another_list_of_names
puts
__END__
Bill ["Fred", "George"] ["Fred", "George"]

super_powers_by_ref.rb

def fetch_super_power_again attrs
  if (power = attrs[:super_power])
    puts power
  else
    puts "couldn't find your super power :/"
  end
end

def fetch_super_power attrs
  attrs.delete(:super_power)
end

attributes = {:name => 'jeff', :super_power => 'flight'}

puts fetch_super_power(attributes) # flight
puts attributes                    # {:name => 'jeff'}
fetch_super_power_again attributes # couldn't find your super power :/