Dependency issue with conda, pip and virtualenv - pip

Question

I am using conda(anaconda 2). Before installing anaconda, my Ubuntu16.04 already had pip installed. I recently installed virtualenv using pip install virtualenv. I did the following steps while trying to install coala in my virtual environment.
Create a new virtual environment using virtualenv venv
Activate environment using source activate path/to/activate
Clone the coala repository.
Run pip3 install -e . while inside the repository
After all this, I get the following error from coala:
There is a conflict in the version of a dependency you have installed and the requirements of coala. This may be resolved by creating a separate virtual environment for coala or running `pip install "yapf~=0.14.0"`. Be aware that the latter solution might break other python packages that depend on the currently installed version.
I am already in a virtualenv, so I tried installing yapf as per the command: pip install "yapf~=0.14.0". After that, when I check my pip list, it still showed yapf (0.15.2), To solve this, I did:
pip uninstall yapf
pip install "yapf~=0.14.0"
Now when I check my pip list, I get the desired results. BUT, the error is still there. It still shows the same dependency error. I am unable to understand what is happening? Which pip is installing what and where, what is conda doing behind the scenes, how is virtualenv behaving with conda, and the most important, why this error and how to resolve it?

Answer 1

first create a virtualenv pertaining to python3.x
template
virtualenv -p {location of python3 version } {name of virtualenv folder}
like this
virtualenv -p /usr/local/bin/python3 venv
then activate it
source venv/bin/activate
then run
pip install {library you want to use}
pip install "yapf~=0.14.0"
This should install yapf into the venv folder.
try that let us know.

Answer 2

Answering my own question, what I found out was that conda and virtualenv do not go hand in hand. condas has the ability to create it's own virtual environment, and if using condas, we must create a conda virtual environment(See this answer).
What I did was uninstalled conda and make a virtual environment using virtualenv. What I could have done as well is uninstall virtualenv and create condas environment and work in that.