Python is readable

Steve Howell showell30 at
Wed Mar 21 05:58:14 CET 2012

On Mar 20, 9:16 pm, Chris Angelico <ros... at> wrote:
> On Wed, Mar 21, 2012 at 1:44 PM, Steve Howell <showel... at> wrote:
> > I think it's a matter of perspective, so there's no right answer, but
> > I always think of the program object as also being the grammatical
> > object, with the implied subject/actor being Python itself.  For
> > example, consider this code:
> >  stack.push(item)
> > It's not the stack that's pushing.  It's the stack being pushed on
> > to.
> In code, though, the push() method is defined in and on the stack
> object (or more likely, on the class that instantiated it, but near
> enough). [...]

The interpretation that the "subject" is the Stack class itself leads
to this coding style:

   Stack.push(stack, item)

The above code takes duck-typing to an extreme--you don't have to
assume that "stack" was instantiated from "Stack" in order to apply
"Stack.push" to "stack" (where "Stack" acts a the subject and "stack"
acts as a grammatical direct object).

Of course, 99% of the time, we want some sugar that makes Stack be the
implicit subject (given that "stack" was instantiated from "Stack"):

  stack.push(item) # push comes from Stack via stack

> Yes, the implied subject could be the
> language interpreter; but it could just as easily be the CPU, or those
> friendly nanobots, or that guy moving the rocks in XKCD 505. But in
> the abstraction of the line of code, you don't care how CPython goes
> about loading globals, calling bound methods, and incrementing object
> reference counts - you just care that the stack is pushing this item
> onto itself.

Sure, that's all good, but, colloquially, I bet you've probably said
at one time in your life, "And, here, we are pushing the item on to
the stack."  The subject is vague ("we"), but there is no assumption
of friendly nanobots (or vigorous hamsters, or CPUs, or any specific
mechanisms), just the idea that the stack is the object, not the

> Some method names are definitely written as though their primary
> argument is the object, not the subject. Either option works. Do you
> think about code as the subject+verb and a data structure as the
> object, or the object as the subject and the method as the verb?
> Fundamentally no difference.

At a certain fundamental level, sure, of course it's all just data
structure and code, so we shouldn't be quibbling about syntax or
grammar, and we certainly shouldn't be throwing around strained
analogies to natural languages.

But in this context, we are musing about grammar, so I would propose
this question:

   What's more important, the object or the method?

IMHO the method is usually more interesting than the object itself.
Of course, the "stack" itself is important, but on any given line of
code, the action is more interesting, so I'd want to lead with "push"
or "pop."

Verb-first gets a bad rap, because people tend to associate verb-first
syntax with early, primitive imperative/functional languages that had
no OO syntax.

Assembly tends to be very imperative:


So saying "push(stack, item)" or "push(item, stack)" seems very
unsophisticated, almost assembly-like in syntax, albeit at a higher
level conceptually than assembly.

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