Why is foo: 1:2:3:4 an integer in yaml?

Hi, I am trying to figure out an oddity (at least to me) in YAML. Why is 
foo: 1:2:3:4 seen as an integer and what is it doing to calculate? It is 
different between languages as seen below:

Ruby:
irb(main):003:0> YAML.load('foo: 1:2:3:4')
=> {"foo"=>3963}

Python:
 >>> print yaml.load('foo: 1:2:3:4')
 >>> {'foo': 223384}


Thanks.



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