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Re: PyWart: "Python's import statement and the history of external dependencies"

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On Thu, Nov 20, 2014 at 8:53 PM, Rick Johnson
<rantingrickjohnson@gmail.com> wrote:
> FOR INSTANCE: Let's say i write a module that presents a
> reusable GUI calendar widget, and then i name the module
> "calender.py".
>
> Then Later, when i try to import *MY* GUI widget named
> "calendar", i will not get *MY* calendar widget, no, i will
> get the Python calendar module.

Because like a fool you created a local module with a totally generic
name like "calendar" and dumped it into the top-level namespace. The
Python import system gives you the ability to create packages, so use
them -- create a package to contain all the widgets you create. If
they're only for your own use, then you can just call it ricklib or
anything else you want.  Then your import becomes:

import ricklib.calendar  # or from ricklib import calendar

Now you can drop as much stuff in there as you like, and none of it
will ever conflict with the standard library (unless a standard
"ricklib" module is added, which is unlikely).

> The reason Python finds the library module instead of my
> module is because the Python library is higher in search
> path than my module.

Your PYTHONPATH is added to the sys.path before the Python library,
not after, so to the extent that there is an issue, it's actually the
other way around. You would get your local calendar module when trying
to import the system calendar module.

> # Contrary to popular belief, sys.path is *NOT* a module,  #
> # no, it's a global!                                       #

I really doubt that this is a popular belief.

> This is another confusing fundamental of Python, it seems *MORE*
> intuitive that changes to the "import search path" would only
> affect the *CURRENT* module's "import search path", but that's
> is not the case!

This just seems like it would create a maintenance nightmare. Before
you could import anything, you'd have to figure out what the search
path is for the particular module you're working and whether it
happens to include the particular package you want. You find it
doesn't, so you make a local change to the search path. Later, you
make the same change to other modules that need to import it. Later
still, the package moves to a different location in the file system,
and now you get to go through and update every one of those modules
with the new directory. Lucky you.

And after all that, it would still fail if you happened to want to
import both "calendar" modules into the same module.

> in the 25% of cases where *NAME SHADOWING* or where the
> author knows the location and can specify the location to
> save "lobby boy" from knocking on doors until his knuckles
> bleed, the author should have an option defining the search
> path *LOCALLY* (in a manner that will *NOT* affect the
> "import search path" further down the import chain), WITHOUT
> needing to import one of the many discombobulated and
> confusing import tools that Python has tortured this
> community with.

By doing so, the author would also make the module non-portable. This
is a major problem if they intend to distribute it, but still a
problem even if they don't. Any time the code is moved to a new system
and placed in a new location (or worse: moved to a new operating
system) the code will have to be updated. And you can pretty much
forget about hosting it on a network share.

>> 3) Filepath imports (deprecated in 3.4 but under discussion for
>> reprecation or replacement)
>>
>>      import importlib.machinery
>>
>>      loader = importlib.machinery.SourceFileLoader("module.name",
>>          "/path /to/file.py")
>>      foo = loader.load_module()
>>      foo.MyClass()
>
> That's ridiculously noisy. I have an idea, if you *REALLY*
> want to introduce boilerplate hell then Python should adopt
> "import header files", NOT!

It's three lines of code to replace one. Two if you exclude the
importlib.machinery import that doesn't need to be repeated.  Is this
really any worse than something like:

local_search_path.insert(0, "/path/to/local/module")
import my_local_module

that you are proposing?

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PyWart: "Python's import statement and the history of external dependencies" Rick Johnson <rantingrickjohnson@gmail.com> - 2014-11-15 21:01 -0800
  Re: PyWart: "Python's import statement and the history of external dependencies" Chris Angelico <rosuav@gmail.com> - 2014-11-16 16:16 +1100
  Re: PyWart: "Python's import statement and the history of external dependencies" alex23 <wuwei23@gmail.com> - 2014-11-21 10:14 +1000
    Re: PyWart: "Python's import statement and the history of external dependencies" Chris Angelico <rosuav@gmail.com> - 2014-11-21 11:31 +1100
    Re: PyWart: "Python's import statement and the history of external dependencies" Rick Johnson <rantingrickjohnson@gmail.com> - 2014-11-20 19:53 -0800
      Re: PyWart: "Python's import statement and the history of external dependencies" Tim Chase <python.list@tim.thechases.com> - 2014-11-21 04:26 -0600
        Re: PyWart: "Python's import statement and the history of external dependencies" Rick Johnson <rantingrickjohnson@gmail.com> - 2014-11-21 07:52 -0800
          Re: PyWart: "Python's import statement and the history of external dependencies" Tim Chase <python.list@tim.thechases.com> - 2014-11-21 10:12 -0600
          Re: PyWart: "Python's import statement and the history of external dependencies" Ian Kelly <ian.g.kelly@gmail.com> - 2014-11-21 10:42 -0700
      Re: PyWart: "Python's import statement and the history of external dependencies" Ned Batchelder <ned@nedbatchelder.com> - 2014-11-21 06:32 -0500
      Re: PyWart: "Python's import statement and the history of external dependencies" Ian Kelly <ian.g.kelly@gmail.com> - 2014-11-21 08:33 -0700
        Re: PyWart: "Python's import statement and the history of external dependencies" Rick Johnson <rantingrickjohnson@gmail.com> - 2014-11-21 10:24 -0800
          Re: PyWart: "Python's import statement and the history of external dependencies" Chris Angelico <rosuav@gmail.com> - 2014-11-22 05:34 +1100
          Re: PyWart: "Python's import statement and the history of external dependencies" Michael Torrie <torriem@gmail.com> - 2014-11-21 12:05 -0700
            Re: PyWart: "Python's import statement and the history of external dependencies" Rick Johnson <rantingrickjohnson@gmail.com> - 2014-11-21 12:29 -0800
              Re: PyWart: "Python's import statement and the history of external dependencies" Michael Torrie <torriem@gmail.com> - 2014-11-21 15:54 -0700
          Re: PyWart: "Python's import statement and the history of external dependencies" Ian Kelly <ian.g.kelly@gmail.com> - 2014-11-21 12:23 -0700
            Re: PyWart: "Python's import statement and the history of external dependencies" Rick Johnson <rantingrickjohnson@gmail.com> - 2014-11-21 14:25 -0800
              Re: PyWart: "Python's import statement and the history of external dependencies" Rick Johnson <rantingrickjohnson@gmail.com> - 2014-11-21 15:21 -0800
                Re: PyWart: "Python's import statement and the history of external dependencies" Chris Angelico <rosuav@gmail.com> - 2014-11-22 10:52 +1100
                Re: PyWart: "Python's import statement and the history of external dependencies" Rick Johnson <rantingrickjohnson@gmail.com> - 2014-11-21 17:07 -0800
                Re: PyWart: "Python's import statement and the history of external dependencies" Chris Angelico <rosuav@gmail.com> - 2014-11-22 13:36 +1100
                Re: PyWart: "Python's import statement and the history of external dependencies" Ian Kelly <ian.g.kelly@gmail.com> - 2014-11-22 02:27 -0700
                Re: PyWart: "Python's import statement and the history of external dependencies" sohcahtoa82@gmail.com - 2014-11-21 16:33 -0800
                Import a module from a specific file path (was: PyWart: "Python's import statement and the history of external dependencies") Ben Finney <ben+python@benfinney.id.au> - 2014-11-22 11:37 +1100
                Re: Import a module from a specific file path Marko Rauhamaa <marko@pacujo.net> - 2014-11-22 08:28 +0200
                Re: Import a module from a specific file path (was: PyWart: "Python's import statement and the history of external dependencies") Chris Angelico <rosuav@gmail.com> - 2014-11-22 13:32 +1100
                Re: Import a module from a specific file path Ben Finney <ben+python@benfinney.id.au> - 2014-11-22 17:46 +1100
              Re: PyWart: "Python's import statement and the history of external dependencies" Ian Kelly <ian.g.kelly@gmail.com> - 2014-11-21 17:32 -0700
                Re: PyWart: "Python's import statement and the history of external dependencies" Rick Johnson <rantingrickjohnson@gmail.com> - 2014-11-21 17:48 -0800
          Re: PyWart: "Python's import statement and the history of external dependencies" Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2014-11-21 15:38 -0500
        Re: PyWart: "Python's import statement and the history of external dependencies" Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-11-22 23:25 +1100
          Re: PyWart: "Python's import statement and the history of external dependencies" Chris Angelico <rosuav@gmail.com> - 2014-11-23 00:00 +1100
            Re: PyWart: "Python's import statement and the history of external dependencies" Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-11-23 17:30 +1100
              Re: PyWart: "Python's import statement and the history of external dependencies" Rustom Mody <rustompmody@gmail.com> - 2014-11-22 22:44 -0800
              Re: PyWart: "Python's import statement and the history of external dependencies" Chris Angelico <rosuav@gmail.com> - 2014-11-23 17:56 +1100
              Re: PyWart: "Python's import statement and the history of external dependencies" Chris Angelico <rosuav@gmail.com> - 2014-11-23 17:59 +1100
                Re: PyWart: "Python's import statement and the history of external   dependencies" Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2014-11-24 11:37 +1300
                Re: PyWart: "Python's import statement and the history of external dependencies" Rick Johnson <rantingrickjohnson@gmail.com> - 2014-11-23 22:25 -0800
                Re: PyWart: "Python's import statement and the history of external dependencies" Chris Angelico <rosuav@gmail.com> - 2014-11-24 17:34 +1100
                Re: PyWart: "Python's import statement and the history of external dependencies" Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-11-24 10:34 +0000
                Re: PyWart: "Python's import statement and the history of external dependencies" Rick Johnson <rantingrickjohnson@gmail.com> - 2014-11-24 08:51 -0800
                Re: PyWart: "Python's import statement and the history of external dependencies" Ned Batchelder <ned@nedbatchelder.com> - 2014-11-24 12:06 -0500
                Re: PyWart: "Python's import statement and the history of external dependencies" Robin Becker <robin@reportlab.com> - 2014-11-24 17:07 +0000
                Re: PyWart: "Python's import statement and the history of external dependencies" Marko Rauhamaa <marko@pacujo.net> - 2014-11-24 19:08 +0200
                Re: PyWart: "Python's import statement and the history of external dependencies" Rustom Mody <rustompmody@gmail.com> - 2014-11-24 09:38 -0800
                Re: PyWart: "Python's import statement and the history of external dependencies" Ian Kelly <ian.g.kelly@gmail.com> - 2014-11-24 15:34 -0700
              Re: PyWart: "Python's import statement and the history of external dependencies" Ben Finney <ben+python@benfinney.id.au> - 2014-11-23 18:43 +1100
              Re: PyWart: "Python's import statement and the history of external dependencies" Chris Angelico <rosuav@gmail.com> - 2014-11-23 18:51 +1100
              Re: PyWart: "Python's import statement and the history of external dependencies" Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2014-11-23 11:23 -0500
              Re: PyWart: "Python's import statement and the history of external dependencies" Chris Angelico <rosuav@gmail.com> - 2014-11-24 03:36 +1100
          Re: PyWart: "Python's import statement and the history of external dependencies" Tim Chase <python.list@tim.thechases.com> - 2014-11-22 15:27 -0600
            Re: PyWart: "Python's import statement and the history of external dependencies" Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-11-23 12:00 +1100
              Re: PyWart: "Python's import statement and the history of external dependencies" Tim Chase <python.list@tim.thechases.com> - 2014-11-22 19:33 -0600

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