The Python design FAQ explains why Len is a built-in function instead of a method. Guido wanted a guarantee that whenever he called it, it'd return a whole number. As just another method, you might find a new type that defines a length in fractional terms, which would break any code wanting to use that as a list index, etc.

But that would be on your for misusing the length method. All the built-in and popular libraries would still define length properly.

Perhaps, but "your" mistake might impede the popularity of the language. A wide range of well-designed community libraries are a major reason to choose Python.

Take a look at the design rationale for the new __matmul__ magic method. It's not for the standard library, it's for the community.

The need to do that reveals a couple of weaknesses (or more charitably, tradeoffs) of Python: lack of type constraints, and (related) lack of well-defined, invariant interfaces on objects.

Trade-offs indeed. Magic methods indicate the use of interfaces defined by traits rather than formal types. Duck Typing. It's flexible.

But you can also see that Guido has been into types lately. He's been pushing the development of mypy and the new optional type system.

Ruby is just used rarely outside RoR, realistically speaking.

Actually, you should qualify that a bit more. Ruby is rarely used outside of Ruby on Rails in North America. In Japan, it is widely used and Ruby on Rails is fair less common.

What were Ruby used for in japan?

Ruby is a very versatile language in its own right. While the other poster is correct that it is used for anything that perl and python are used for it's also taking a large chunk from the Java and C# crowd in Japan. Everything from server side applications to command line tools and even GUI based desktop applications can be written in Ruby. Using FFI I have made some quite amazing applications with Ruby.

Rails is amazing and I personally love it. But it's not the only thing Ruby is good for.

Probably anything that Perl and Python are used for.

Well, true, you have a point. Ruby is rarely used outside of Rails. Which is a shame, really.

Go to Japan.

Whitespace is no issue with a good editor (Sublime, vim, emacs...).

I dislike the many inconsistencies in Python. You mentioned one. Others: sort vs sorted (destructive vs non destructive). Also: not being able to chain methods because many don't return a value. (Scheme, Elixir or even Ruby are imho much more elegant.)

But all in all Python is a very useful programming language with a rich eco system.

The Python design FAQ explains that .append and .sort return None to remind you they are mutation methods. I find this more elegant than Ruby, etc., where many things look like pure functions but aren't.

https://docs.python.org/2/faq/design.html#why-doesn-t-list-s...

I know the reasons why and how mutating methods work in Python.

Nevertheless I find this here much more elegant:

data.sort.tail.first # or this data.append(7).append(3)

More elegant than this:

sorted(data)[1:][0]

data.append(7) # and then

data.append(3)

I love method chaining in Elixir or Javascript. In Python I have to create temp variables here and there to capture / further process intermediate results.

Having said that: Python has it's strengths. I use it more than any other programming language.

I understand the preference and the difficulty created by methods and operators that are essentially statements instead of expressions. However, when making that criticism we should also acknowledge the benefit of requiring or encouraging multiple lines for those actions.

    if (x=42) {}

Has burned many people. Append having a useful return is comparable, though probably not as much of a trap.

> sorted(data)[1:][0]

I don't want to get into the weeds, but shouldn't that just be

    sorted(data)[1]

Or if you like unpacking for clarity

    first, second = sorted(data)[:2]

?