Are there something like Python generators in Ruby?

Question

Ruby’s yield keyword is something very different from the Python keyword with the same name, so don’t be confused by it. Ruby’s yield keyword is syntactic sugar for calling a block associated with a method.

The closest equivalent is Ruby’s Enumerator class. For example, the equivalent of the Python:

def eternal_sequence():
  i = 0
  while True:
    yield i
    i += 1

is this:

def eternal_sequence
  Enumerator.new do |enum|
    i = 0
    while true
      enum.yield i # <- Notice that this is the yield method of the enumerator, not the yield keyword
      i +=1
    end
  end
end

You can also create Enumerators for existing enumeration methods with enum_for. For example, ('a'..'z').enum_for(:each_with_index) gives you an enumerator of the lowercase letters along with their place in the alphabet. You get this for free with the standard Enumerable methods like each_with_index in 1.9, so you can just write ('a'..'z').each_with_index to get the enumerator.

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