How to get second init.py execute for same namespace

Question

Here is my directory structure

.
|-- path1
|   `-- mynms
|       |-- __init__.py
|       `-- app1
|           |-- __init__.py
|           `-- foo.py
|-- path2
|   `-- mynms
|       |-- __init__.py
|       `-- app2
|           |-- __init__.py
|           `-- bar.py
`-- user.py

File contents:

$ cat user.py
#!/usr/bin/python

import sys
sys.path.append('path1')
sys.path.append('path2')

from mynms.app2.foo import foo
from mynms.app2.bar import bar

foo()
bar()

$ cat path1/mynms/__init__.py;echo ==============;cat path2/mynms/__init__.py
from pkgutil import extend_path
__path__ = extend_path(__path__, __name__)

print "I am path1/mynms/__init__.py"
==============
from pkgutil import extend_path
__path__ = extend_path(__path__, __name__)

print "I am path2/mynms/__init__.py"

$ cat path1/mynms/app1/foo.py; echo ============; cat path2/mynms/app2/bar.py
def foo():
  print "foo!"
============
def bar():
  print "bar!"

Question: When I run user.py, I get only the output of path1/__init__.py but not for path2. Is there some way to fix that?

$ ./user.py
I am path1/mynms/__init__.py        -----> Why is 'I am path2/mynms/__init__.py not printed?
foo!
bar!

You have two packages with the same name which is generally frowned upon. Any reason why your test case package has to be the same name? Can you just rename that second one? — tdelaney
– tdelaney, Commented Jun 25, 2014 at 17:10
I can't change them to different namespaces for other reasons. They are two apps by same dev team but has to stay in different hierarchy for deployment purposes. — balki
– balki, Commented Jun 25, 2014 at 17:20
Python 2 does not support namespaced packages out of the box. setuptools does add namespace support, but to replicate that behaviour requires extensive hacking. I can summarise what setuptools does at some point when I have more time, but you may as well use it directly to package up your projects and have setuptools manage the namespacing for you. — Martijn Pieters
– Martijn Pieters, Commented Jun 27, 2014 at 23:20

r3m0t · Accepted Answer · 2014-06-27 21:13:41Z

When you write import mynms.app2.foo or from mynms.app2.foo import foo, Python does this:

import mynms by looking for the file mynms/__init__.py, which it finds in path1
import mynms.app1 by looking for a file mynms/app1/__init__.py (or mynms/app1.py)
import mynms.app1.foo by looking for mynms/app1/foo.py (or mynms/app1/foo/__init__.py)

On the next import statement, import mynms.app2.bar, Python does:

import mynms - it's already imported so there's nothing to do. (You can check sys.modules['mynms'] to see whether it is already imported. If it isn't, it will raise KeyError.)
import mynms.app2 - again, this is already imported.
import mynms.app2.bar by reading the file mynms/app2/bar.py, which is in path2

There's no (sensible) way for Python to import the mynms module twice from two different files.

If you have initialisation code you will need to put them in the modules mynms.app1 and mynms.app2 so they have different names. i.e. the files mynms/app1/__init__.py and mynms/app2/__init__.py.

newtover · Accepted Answer · 2014-07-03 15:26:06Z

As Martijn Pieters has already mentioned in comments, Python 2 does not support packages distributed as a collection of packages. But you can emulate such packages if you use setuptools (most probably you do).

The only problem is that the packages should have correct metainformation, so that setuptools could join several subpackages in a virtual single package. The information is usually passed to setup() function in setup.py and lives in your site-packages directory after the installation. That means that those who distribute the packages should anyway make something to properly prepare them, and you can hardly just put them in PATH to make them work.

Here is the link to the corresponding documentation. Be ready to spend some time, because PEAK documentation is not always enough for a quick start.

Rachel Sanders · Accepted Answer · 2014-06-27 21:41:09Z

0

I agree with the rest of the comments - this is bad code structure and should be refactored ASAP. However, if you really, really, really can't or can't yet, then you can muck with the import internals by using the imp module in the standard library:

https://docs.python.org/2/library/imp.html

For example, you can import a file not in your normal python module search path by doing something like:

/Users/me/test.py:

def run_foo():
  print "hi got here"

and another script:

import imp
foo = imp.load_source("foo", "/Users/me/test.py")
foo.run_foo()

Again, you're working against Python doing it this way, not with it. But it is a good trick to know.

answered Jun 27, 2014 at 21:41

Rachel Sanders

5,8941 gold badge30 silver badges36 bronze badges

Collectives™ on Stack Overflow

How to get second init.py execute for same namespace

3 Answers 3

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related