How to list available versions of a Pypi package

While working on requirements that someone had for a pypi package, I found myself needing to list out the versions of the package that were available.  I didn't want to have to go to the pypi website, navigate to the package and then figure out how to see the available versions.  So, to the Googles I went.

In order to install a specific version of a package, you would run:

pip install =1.0.0

in order to install version 1.0.0 of said package.  But, if you provide nonsense as the option, like so:

pip install =blah

then what you get back is an error listing all of the available versions for that package:

> pip install mod_wsgi==blah
Collecting mod_wsgi==blah
Could not find a version that satisfies the requirement mod_wsgi==blah (from versions: 4.1.0, 4.1.1, 4.1.2, 4.1.3, 4.2.0, 4.2.1, 4.2.2, 4.2.3, 4.2.4, 4.2.5, 4.2.6, 4.2.7, 4.2.8, 4.3.0, 4.3.1, 4.3.2, 4.4.0, 4.4.1, 4.4.2, 4.4.3, 4.4.4, 4.4.5, 4.4.6, 4.4.7, 4.4.8, 4.4.9, 4.4.10, 4.4.11, 4.4.12, 4.4.13, 4.4.14, 4.4.15, 4.4.16, 4.4.17, 4.4.18, 4.4.19, 4.4.20, 4.4.21, 4.4.22, 4.4.23, 4.5.0, 4.5.1, 4.5.2, 4.5.3, 4.5.4, 4.5.5, 4.5.6, 4.5.7, 4.5.8, 4.5.9, 4.5.10, 4.5.11, 4.5.12, 4.5.13, 4.5.14, 4.5.15, 4.5.16, 4.5.17, 4.5.18, 4.5.19, 4.5.20, 4.5.21, 4.5.22, 4.5.23, 4.5.24, 4.6.0, 4.6.1, 4.6.2, 4.6.3, 4.6.4)
No matching distribution found for mod_wsgi==blah

Good to know its that easy.

python pip throwing SSL: TLSV1 alert (SOLUTION)

I recently ran into an issue with Python pip, where I attempted to run a 'pip install' of a module and was presented with the following error:

> pip install pymongo
Collecting pymongo
Could not fetch URL https://pypi.python.org/simple/pymongo/: There was a problem confirming the ssl certificate: [SSL: TLSV1_ALERT_PROTOCOL_VERSION] tlsv1 alert protocol version (_ssl.c:590) - skipping
Could not find a version that satisfies the requirement pymongo (from versions: )
No matching distribution found for pymongo

No matter what I did (install, update and even just search the pip repository) I was presented with this same error.  It was certainly a hard, fast stop to whatever I was attempting to do.

But, after some googling and reading of many people's accounts of their trials and tribulations attempting to solve it, I finally found a solution that works.  I happened upon the this posting on StackOverflow, which leads you to the fact that you have to upgrade pip.  Unfortunately, attempting to upgrade it with itself will fail as above.  But, you should instead run the following:

curl https://bootstrap.pypa.io/get-pip.py | python

That upgraded pip directly from the website using its install script.  It is a work around, yes, but one that seems to have worked for me (and apparently others).  Hopefully this solves your issue(s) as well.

**UPDATE: You will need to run the curl command in each virtualenv environment that you have, as each one will have its own installation of python.

'_remove_dead_weakref' error after upgrading to Ubuntu 17.10

Well, after finally getting my Flask app running and returning data, I upgraded my system to Ubuntu 17.10 (from 17.04).  Today, I tried to start my flask app and was greeted with a bunch of Python error output and the following error:

ImportError: cannot import name '_remove_dead_weakref'

I was baffled as the app worked the day before.  So after some digging around the Googles, I found that the issue was caused by my upgrade to 17.10.

The fix....... delete your virtual environment and rebuild it.  I am not saying delete your project directory, I am saying delete your envs directory (which is where the executables for the virtual environment are.  Some people put it in the same directory.  If you are like me, you have a central location where you keep them. 

You will need to remove that entire directory, rebuild it and then re-run the virtualenv command to create the virtualized environment and then install any modules that you had previously installed (as they get stored in the directory structure you just deleted.  After that, your app and its parts should work fine.

Python pip Broken After Upgrade To OSx El Capitan

Wow its been a long time since I blogged.  I have no excuse other than things have been a touch crazy.  My work recently started allowing us to upgrade our Mac's from Yosemite to El Capitan.  For me the upgrade only took about 45 minutes, which is pretty quick in the grand scheme of things.  The download is a little over 6 gb and went pretty quickly.  

I was going along fine until today when I tried to install a new module using pip.  About 1/2 way through the installation I was presented with the following output:

    In file included from src/lxml/lxml.etree.c:321:
    src/lxml/includes/etree_defs.h:14:10: fatal error: 'libxml/xmlversion.h' file not found
    #include "libxml/xmlversion.h"
             ^
    1 error generated.
    Compile failed: command 'cc' failed with exit status 1
    creating tmp
    cc -I/usr/include/libxml2 -I/usr/include/libxml2 -c /tmp/xmlXPathInitf3OxN6.c -o tmp/xmlXPathInitf3OxN6.o
    /tmp/xmlXPathInitf3OxN6.c:1:10: fatal error: 'libxml/xpath.h' file not found
    #include "libxml/xpath.h"
             ^
    1 error generated.
    *********************************************************************************
    Could not find function xmlCheckVersion in library libxml2. Is libxml2 installed?
    Perhaps try: xcode-select --install
    *********************************************************************************
    error: command 'cc' failed with exit status 1
    ----------------------------------------
Command "/usr/bin/python -u -c "import setuptools, tokenize;__file__='/private/tmp/pip-build-9IduXA/lxml/setup.py';exec(compile(getattr(tokenize, 'open', open)(__file__).read().replace('\r\n', '\n'), __file__, 'exec'))" install --record /tmp/pip-RgavmY-record/install-record.txt --single-version-externally-managed --compile" failed with error code 1 in /private/tmp/pip-build-9IduXA/lxml/

I had installed other modules last week, but then I realized that that was prior to my upgrading.  I looked at the above output and noticed the line:

     Perhaps try: xcode-select --install

OF COURSE!!!  Although I upgraded, and XCode had been upgraded to, I still needed to do some things with XCode to get things going again.  First, I opened XCode and went through its initial startup after an upgrade.  A bunch of clicking and things were good there.  I then opened up my command line and, prefixing the command with 'sudo', I ran the 'xcode-select --install' command from above.  This presented me a pop-up window to install tools.  So, I accepted and allowed it to install.  Once finished, I tried my pip module installation again and VOILA!!!!  It worked!!!

So, in this lesson, always make sure to update your XCode and xcode-select before moving on after an upgrade.

A Couple Of virtualenv Notes

A little while ago I posted about starting a python project, and posted a link to a bitbucket project I posted that can be used to create a virtual environment (and have the environment auto activate upon entering the project directory).  I wanted to post just a couple of things that I learned, one of which bit me a touch when working on a recent python script.

I was working on said script and kept getting erroneous errors.  The errors were not making sense, telling me that the module I was working with was not installed.  I called 'bull' as I know I had installed it in the environment using pip.  Well, I thought I had.  It bit me in that I did not remember that when you are working in a python virtual environment, you NEED to use the pip and python executables installed under the environment (in the environment's bin directory).  If you don't, and just call pip or python, it will reference the system version by default.

This was brought even more to my attention when I ran 'pip freeze' to see what modules I had installed, and the list was looooooong.  I quickly realized that I was not using what I thought I was.  So, always make sure you reference the correct application.   Of course, one gotcha to remember is that once you develop your application, if you move it out of the virtual environment, you need to fix any path's that point to the python interpreter.

Consider that a lesson learned for me.  Hopefully it will allow you to forego learning it too painfully (or just annoyingly).