[issue29258] __init__.py required for pkgutil.walk_packages in python3

[Inada Naoki]

Inada Naoki  added the comment:

I am totally agree with Wolfgang:

> they make it impossible to know whether a directory found on the filesystem 
> is *intended* as a Python package or not.

I think we shouldn't treat normal directory as namespace package until some 
portion in the directory is imported, or it is specified explicitly.

So walk_packages() should be used like:

  walk_packages("/path/to/namespace", "namespace")

I already rejected similar issue: #29642.

If you can not agree with me, please make an thread in python-dev ML or 
discuss.python.org.

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[issue29258] __init__.py required for pkgutil.walk_packages in python3

[Inada Naoki]

Change by Inada Naoki :


--
assignee:  -> docs@python
components: +Documentation -Library (Lib)
nosy: +docs@python
resolution: rejected -> 
stage: resolved -> needs patch
status: closed -> open
versions: +Python 3.8, Python 3.9 -Python 3.5, Python 3.6

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[issue29258] __init__.py required for pkgutil.walk_packages in python3

[Eric Wieser]

Eric Wieser  added the comment:

If the resolution here is that this is behaving as intended (which personally I 
disagree with), I think this issue should remain open as a documentation task - 
the docs should clearly state that this does not apply to PEP420 namespace 
packages.

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[issue29258] __init__.py required for pkgutil.walk_packages in python3

[Inada Naoki]

Inada Naoki  added the comment:

> PEP420 makes __init__.py files optional

This is almost wrong.  PEP 420 added a new way for "namespace pacakge."
PEP 420 doesn't make empty __init__.py file in regular package.

(See https://dev.to/methane/don-t-omit-init-py-3hga)

Then, should pkgutil.walk_packages walk into all directories (e.g.  
node_modules) ?  I don't think so.

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nosy: +inada.naoki
resolution:  -> rejected
stage:  -> resolved
status: open -> closed

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[issue29258] __init__.py required for pkgutil.walk_packages in python3

[Eric Wieser]

Change by Eric Wieser :


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nosy: +Eric Wieser

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[issue29258] __init__.py required for pkgutil.walk_packages in python3

[Brett Cannon]

Changes by Brett Cannon :


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nosy:  -brett.cannon

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[issue29258] __init__.py required for pkgutil.walk_packages in python3

[Wolfgang Maier]

Wolfgang Maier added the comment:

> all that's required here is to eliminate the check for __init__.py from 
> pkgutil._iter_file_finder_modules

Ok, I was exaggerating here. To do it right would require a more complex 
change, but that's all that's needed to get an estimate of the effect the real 
thing would have.

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[issue29258] __init__.py required for pkgutil.walk_packages in python3

[Wolfgang Maier]

Wolfgang Maier added the comment:

While it is rather trivial to implement the proposed functionality - all that's 
required here is to eliminate the check for __init__.py from 
pkgutil._iter_file_finder_modules - this would have undesired impacts on, e.g., 
pydoc.apropos:
This function would then recursively report *any* directory/subdirectory on 
sys.path, which is quite surely not what people want.

I think this is a fundamental problem with namespace packages: they are nice 
and flexible for specific imports, but they make it impossible to know whether 
a directory found on the filesystem is *intended* as a Python package or not.

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[issue29258] __init__.py required for pkgutil.walk_packages in python3

[Wolfgang Maier]

Changes by Wolfgang Maier :


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nosy: +wolma

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[issue29258] __init__.py required for pkgutil.walk_packages in python3

[Serhiy Storchaka]

Changes by Serhiy Storchaka :


--
nosy: +brett.cannon, eric.snow, ncoghlan
versions:  -Python 3.3, Python 3.4

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[issue29258] __init__.py required for pkgutil.walk_packages in python3

[Anthony Sottile]

New submission from Anthony Sottile:

PEP420 makes __init__.py files optional: 
https://docs.python.org/3/whatsnew/3.3.html#pep-420-implicit-namespace-packages

Though it seems without them, pkgutil.walk_packages does not function as 
desired: https://docs.python.org/3/library/pkgutil.html#pkgutil.walk_packages

Consider the following example:

```
$ tree foo
foo
├── bar
│   ├── baz.py
│   └── __init__.py
├── __init__.py
└── womp.py
```

And a test script

# test.py
```
import pkgutil

import foo


for _, mod, _ in pkgutil.walk_packages(foo.__path__, foo.__name__ + '.'):
print(mod)
```

In both python2 and python3 I get the following output:

```
$ python2.7 test.py
foo.bar
foo.bar.baz
foo.womp
$ python3.5 test.py
foo.bar
foo.bar.baz
foo.womp
```

Removing the __init__.py files and only using python3, I get this:

```
$ find -name '__init__.*' -delete
$ python3.5 test.py
foo.bar
```

The modules are definitely importable:

```
$ python3.5 -c 'import foo.bar.baz'
$
```

Originally asked as a question on stackoverflow: 
http://stackoverflow.com/questions/41203765/init-py-required-for-pkgutil-walk-packages-in-python3

--
components: Library (Lib)
messages: 285361
nosy: Anthony Sottile
priority: normal
severity: normal
status: open
title: __init__.py required for pkgutil.walk_packages in python3
type: behavior
versions: Python 3.3, Python 3.4, Python 3.5, Python 3.6, Python 3.7

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