With dynamically typed languages, it is very hard to "be consistent as a method" since there are no tools to enforce that consistency. Social cues usually go 90% of the way, but not all the way whereas a function/generic method handles that just fine: to get a length, you call `len`. Period. The developer does not really have the option to do otherwise, unless he wants to opt out of the language's ecosystem.
Actually what I said above is not entirely true, there is one situation where it is "quite easy" to handle method consistency in a dynamically typed language: when you deal with mixins.
Because mixins have preconditions (methods and/or properties which need to exist for it to work), they enforce those names or they can't be used at all. And of course any method brought in by the mixin is "enforced" by default.
So is it with most things iteration in Ruby for instance: Enumerable mandates that a core internal iterator named `#each` exists (as well as #<=> optionally) and as a reward for doing so it gives about 30 methods "for free". That enforces consistency in collection traversal, because even if you reimplement some or all of these methods in the long term (for efficiency and whatnot) getting them "for free" out of the box is valuable.
