ImportError: No module named attr

Question

I have only very rudimentary experience in Python. I am trying to install the package pyslim (see here on the pypi website). I did

$ pip install pyslim

Requirement already satisfied: pyslim in ./Library/Python/2.7/lib/python/site-packages/pyslim-0.1-py2.7.egg (0.1)
Requirement already satisfied: msprime in /usr/local/lib/python2.7/site-packages (from pyslim) (0.6.1)
Requirement already satisfied: attrs in /usr/local/lib/python2.7/site-packages (from pyslim) (16.3.0)
Requirement already satisfied: svgwrite in /usr/local/lib/python2.7/site-packages (from msprime->pyslim) (1.1.12)
Requirement already satisfied: jsonschema in /usr/local/lib/python2.7/site-packages (from msprime->pyslim) (2.6.0)
Requirement already satisfied: six in /usr/local/lib/python2.7/site-packages (from msprime->pyslim) (1.10.0)
Requirement already satisfied: numpy>=1.7.0 in /usr/local/lib/python2.7/site-packages/numpy-1.10.4-py2.7-macosx-10.11-x86_64.egg (from msprime->pyslim) (1.10.4)
Requirement already satisfied: h5py in /usr/local/lib/python2.7/site-packages (from msprime->pyslim) (2.8.0)
Requirement already satisfied: pyparsing>=2.0.1 in /usr/local/lib/python2.7/site-packages (from svgwrite->msprime->pyslim) (2.2.0)
Requirement already satisfied: functools32; python_version == "2.7" in /usr/local/lib/python2.7/site-packages (from jsonschema->msprime->pyslim) (3.2.3.post2)

But when I open python and try to import pyslim, it fails

> import pyslim

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/remi/Library/Python/2.7/lib/python/site-packages/pyslim-0.1-py2.7.egg/pyslim/__init__.py", line 4, in <module>
    from pyslim.slim_metadata import *       # NOQA
  File "/Users/remi/Library/Python/2.7/lib/python/site-packages/pyslim-0.1-py2.7.egg/pyslim/slim_metadata.py", line 1, in <module>
    import attr
ImportError: No module named attr

So, I did

$ pip install attr
Requirement already satisfied: attr in /usr/local/lib/python2.7/site-packages (0.3.1)

and

$ pip install attrs
Requirement already satisfied: attrs in /usr/local/lib/python2.7/site-packages (16.3.0)

I restarted python and tried to import pyslim again but I keep receiving the same error message. I also tried to download and install the files from github by doing

$ git clone https://github.com/tskit-dev/pyslim.git
$ cd pyslim
$ python setup.py install --user

as indicated here on the pypi website. On this last line of code, I get a long output ending with

Download error on https://pypi.python.org/simple/: [SSL: TLSV1_ALERT_PROTOCOL_VERSION] tlsv1 alert protocol version (_ssl.c:590) -- Some packages may not be found!
No local packages or download links found for attrs
error: Could not find suitable distribution for Requirement.parse('attrs')

---

I am using Python 2.7.10 on a MAC OSX 10.11.6. Not sure if it matter but I usually install things with homebrew. I am using pip 18.1 from /usr/local/lib/python2.7/site-packages/pip (python 2.7).

Edit

$ which python
   /usr/bin/python
$ which pip
   /usr/local/bin/pip

Answer 1

Take a look to this other question that is related to the attrs package.

In your case, you have attr and attrs installed at the same time, and they are incompatible between them, so python is unable to resolve the package name on the import correctly.

You should use attrs only, so try uninstalling attr and try it again:

python -m pip uninstall attr

If, in the future, you need to have some packages incompatibles between them, take a look about using virtual environments in Python, which are really easy to use and will be very useful to play with packages and packages versions without break anything.