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module 'yaml' has no attribute 'FullLoader'

I am seeing the following error:
Traceback (most recent call last):
File "generateLDA.py", line 14, in <module>
config = yaml.load(fp, Loader = yaml.FullLoader)
AttributeError: module 'yaml' has no attribute 'FullLoader'

The FullLoader class is only available in PyYAML 5.1 and later. Version 5.1 was released on March 13, 2019 and has probably not filtered down to many distributions yet.
You can check the version of PyYAML by inspecting yaml.__version__:
Python 2.7.15 (default, Oct 15 2018, 15:24:06)
[GCC 8.1.1 20180712 (Red Hat 8.1.1-5)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import yaml
>>> yaml.__version__
'3.13'
If you are managing packages with pip, you can upgrade to the current release by running:
pip install -U PyYAML

In case someone wants to use older version of yaml(3.1)
import yaml
with open('filename.yaml') as parameters:
my_dict = yaml.safe_load(parameters)
I stumbled upon it while using rospy to run my packages.

pip install --ignore-installed PyYAML

sudo su
pip install --ignore-installed PyYAML -r requirements.txt
It worked perfectly for fail2ban-geo-exporter
Took hours to figure it out, now it runs under root & systemd

pip3 install -U PyYAML
worked for me on Linux machine.
if it was working earlier then please check whether the indentation of the file is somehow messed-up or not.

Import Error after pip install -e

I have cloned a repo (visdom) from github in order to make some contributions. In order to test my contributions, I tried to install the module within a conda env:
$ which pip
/home/jkarimi91/Apps/anaconda2/envs/visdom/bin/pip
$ pip install -e .
Running pip list shows that the module successfully installed:
visdom (0.1.4, /home/jkarimi91/Projects/visdom)
However, when I try to import the module, I receive an import error:
$ which python
/home/jkarimi91/Apps/anaconda2/envs/visdom/bin/python
$ python
Python 2.7.13 |Continuum Analytics, Inc.| (default, Dec 20 2016, 23:09:15)
[GCC 4.4.7 20120313 (Red Hat 4.4.7-1)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
Anaconda is brought to you by Continuum Analytics.
Please check out: http://continuum.io/thanks and https://anaconda.org
>>> import visdom
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ImportError: No module named visdom
>>>

You could use the -t flag is used to tell pip to install the packages into a particular location, however, there actually appears to be an open issue with -t not playing nice with various other flags (and I just confirmed this for the repo in question). Work around this by installing with the git URL syntax, e.g. pip install git+git://github.com/facebookresearch/visdom.git#master#egg=visdom

As pointed out by Jmills comment, the path /home/jkarimi91/Projects/ was not in my python path. Also, as noted by #Jmills answer, using -t does not seem to be a viable option at the moment.
To fix this issue, I did the following:
$ pip uninstall visdom
$ pip install .
This approach needs to be repeated every time I make a change to the code but at least it works.

matplotlib works with default python but not python3.5 on debian

I have this issue. I think it's best described when I show you my bash commands that I used to produce the problem. See here:
josch#oogway:~$ python
Python 2.7.9 (default, Jun 29 2016, 13:08:31)
[GCC 4.9.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import matplotlib
>>> #works
josch#oogway:~$ python3.5
Python 3.5.0 (default, Apr 26 2017, 21:03:53)
[GCC 4.9.2] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import matplotlib
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ImportError: No module named 'matplotlib'
>>> #what??
Matplotlib was installed by:
sudo apt-get install python-matplotlib
The "default" python came with my OS installation, python3.5 was downloaded and then compiled/installed from source.
Can anyone help? Tried to solve it myselve for 2 hours now but google can't find answer
Edit: I'm trying to install a "second pip" that works with my second installation of Python, which is Python3.5. My default-Python that is managed by the OS is Python 2.7.9. Now, as suggested I did:
joschua#oogway:~/Downloads$ wget https://bootstrap.pypa.io/get-pip.py
and then:
python3.5 get-pip.py
which gave me:
joschua#oogway:~/Downloads$ python3.5 get-pip.py
Traceback (most recent call last):
File "get-pip.py", line 20061, in <module>
main()
File "get-pip.py", line 194, in main
bootstrap(tmpdir=tmpdir)
File "get-pip.py", line 82, in bootstrap
import pip
zipimport.ZipImportError: can't decompress data; zlib not available

Try installing pip3 with:
sudo apt-get install python3-pip
and then try installing matplotlib with:
sudo pip3 install matplotlib

I actually could solve the problem now.
See this link for a reasonable description on how to run two different versions of python on the same system (and as #Pierre de Buyl suggested) use two different pip versions on the same system
https://www.linkedin.com/pulse/20140815081557-89781742-how-to-install-and-use-python-with-different-versions-on-same-linux-machine

So, you installed python3.5 from source. What version of Debian are you using? (I suppose Jessie).
If you want to install packages for this Python interpreter, you must have a pip that actually uses it. Two solutions:
It is installed. If so,
python3.5 -m pip
will work and you can install packages with
python3.5 -m pip install matplotlib
or
python3.5 -m pip install --user matplotlib
It is not installed. You must install it following the instructions at https://packaging.python.org/installing/#requirements-for-installing-packages
apt-get will not install the appropriate pip for your needs. It will only install a pip that is related to the python3 (3.4 for jessie I believe) that is also in the apt-get system.
EDIT: in light of the update, you need also to re-compile python3.5 with zip enabled.

python package installed but could not import

I have tried to re-install and got the following message:
Requirement already satisfied: troposphere==1.8.2 in /usr/local/lib/python2.7/site-packages (from -r requirements.txt (line 13)
I checked my python version and I could see this as same:
animjain$ python -V
Python 2.7.10
When I try to import a module, get the following error:
animjain$ python
Python 2.7.10 (default, Oct 23 2015, 19:19:21)
[GCC 4.2.1 Compatible Apple LLVM 7.0.0 (clang-700.0.59.5)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> from troposphere import Join, Ref, FindInMap
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ImportError: No module named troposphere

You should use virtualenv to install dependencies for your project. You don't need to clog global site-packages.
For example:
sudo apt-get install virtualenv
cd ~
virtualenv your_test_venv
source your_test_venv/bin/activate
pip install troposphere
After that you can use your new package.
When you want to deactivate your virtualenv you can run command deactivate

In case you have multiple Python versions on your machine, install with the same Python command, so instead of:
animjain$ pip install troposphere==1.8.2
run:
animjain$ python -mpip install troposphere==1.8.2

'pip3 --version' failing with a SyntaxError

This all began when I set out to install the Requests library for Python 3 (I'm running on OSX Mavericks with Python 2.7.5 (installed by brew install python) and 3.4.2 (installed by brew install python3). When I run pip3 --version (or anything related to the pip3 command) I see this:
$ pip3 --version
Traceback (most recent call last):
File "/usr/local/bin/pip3", line 7, in <module>
from pip import main
File "/usr/local/lib/python3.4/site-packages/pip/__init__.py", line 11, in <module>
from pip.vcs import git, mercurial, subversion, bazaar # noqa
File "/usr/local/lib/python3.4/site-packages/pip/vcs/mercurial.py", line 9, in <module>
from pip.download import path_to_url
File "/usr/local/lib/python3.4/site-packages/pip/download.py", line 22, in <module>
from pip._vendor import requests, six
File "/usr/local/lib/python3.4/site-packages/pip/_vendor/requests/__init__.py", line 53, in <module>
from .packages.urllib3.contrib import pyopenssl
File "/usr/local/lib/python3.4/site-packages/pip/_vendor/requests/packages/urllib3/contrib/pyopenssl.py", line 49, in <module>
from ndg.httpsclient.ssl_peer_verification import SUBJ_ALT_NAME_SUPPORT
File "/usr/local/Cellar/python3/3.4.2_1/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/ndg/httpsclient/ssl_peer_verification.py", line 17
except ImportError, e:
^
SyntaxError: invalid syntax
When I run the Python 2.7.5 version I see this:
$ pip --version
pip 1.5.6 from /Library/Python/2.7/site-packages/pip-1.5.6-py2.7.egg (python 2.7)
Just for sanity purposes Here is what when I see when I enter the interactive interpreters:
$ python3
Python 3.4.2 (default, Oct 19 2014, 17:52:17)
[GCC 4.2.1 Compatible Apple LLVM 6.0 (clang-600.0.51)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> exit()
$ python
Python 2.7.5 (default, Mar 9 2014, 22:15:05)
[GCC 4.2.1 Compatible Apple LLVM 5.0 (clang-500.0.68)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> exit()
A lot of the other answers related to updating pip3 suggest that I update pip3 with this commend pip3 install --upgrade pip which gives the same error, or I use easy_install -U pip but because of how brew sets up the Pythons, it only updates the Python 2.7.5 version (there is no easy_install3). Any ideas?

The root problem is that you somehow got a Python 2.x-only package installed into your 3.x site-packages.
Underlying that, you've actually got two different Python 2.7 installations (Apple's and Homebrew's) crossed with each other, which may have something to do with how you got a 2.7 package into 3.x as well…
Anyway, the reason this is breaking pip is that pip has various optional dependencies that it tries to import if present, and some of them do the same, and so on, and ultimately, starting up pip is importing the ndg-httpsclient package.
I'm not sure how you got that package. A standard Homebrew 3.x looks in two extra site-packages directories (fire up python3 then import sys; print(sys.path) to see all of the places it looks, both stdlib and site) beyond the one that pip3 installs into.
In this case, you've somehow installed the 2.x version of ndg-httpsclient into /usr/local/Cellar/python3/3.4.2_1/Frameworks/Python.framework/Versions/3.4/lib/‌​python3.4/site-packages.
Since you didn't install it with pip—and, more to the point, since you can't run pip in the first place—you can't just pip uninstall it. So:
rm -rf /usr/local/Cellar/python3/3.4.2_1/Frameworks/Python.framework/Versions/3.4/lib/‌​python3.4/site-packages/ndg*
This could break some other packages that depend on it. Once you get things working, you can use pip3 list to see all the site packages you've installed and test them out. If you want to be paranoid, do something like this:
$ pip3 list > mypackages
$ rm -rf <each site-package directory>
$ brew uninstall python3
$ brew install python3
$ pip3 install -r mypackages
You might want to similarly clean up your Homebrew 2.7 (or just scrap it and only use Apple's—especially since I'm pretty sure you're running Apple's anyway), and the site-packages for the Apple 2.7 (but not Apple's Python itself, of course, because you can't uninstall that).