Download and install openCV 3.1 on Ubuntu 16.04 for Python 2 (no virtualenv)

ocv.sh

#!/bin/bash

sudo apt-get -y update
sudo apt-get -y upgrade

sudo apt-get install -y build-essential cmake pkg-config

sudo apt-get install -y libjpeg8-dev libtiff5-dev libjasper-dev libpng12-dev

sudo apt-get install -y libavcodec-dev libavformat-dev libswscale-dev libv4l-dev
sudo apt-get install -y libxvidcore-dev libx264-dev

sudo apt-get install -y libgtk-3-dev
sudo apt-get install -y libatlas-base-dev gfortran
sudo apt-get install -y python2.7-dev python3.5-dev

cd ~
git clone https://github.com/opencv/opencv.git
git clone https://github.com/opencv/opencv_contrib.git

sudo pip install numpy

cd ~/opencv
mkdir build
cd build
# CPU only:
cmake -D CMAKE_BUILD_TYPE=RELEASE \
    -D CMAKE_INSTALL_PREFIX=/usr/local \
    -D INSTALL_PYTHON_EXAMPLES=ON \
    -D INSTALL_C_EXAMPLES=OFF \
    -D OPENCV_EXTRA_MODULES_PATH=~/opencv_contrib/modules \
    -D BUILD_EXAMPLES=ON ..

# For CUDA support:
# cmake -D CMAKE_BUILD_TYPE=RELEASE \
# 	-D WITH_TBB=ON \
# 	-D WITH_V4L=ON \
# 	-D WITH_QT=ON \
# 	-D WITH_OPENGL=ON \
# 	-D WITH_CUBLAS=ON \
# 	-D CUDA_NVCC_FLAGS="-D_FORCE_INLINES" \
# 	-D CMAKE_INSTALL_PREFIX=/usr/local \
# 	-D INSTALL_PYTHON_EXAMPLES=ON \
# 	-D INSTALL_C_EXAMPLES=OFF \
# 	-D OPENCV_EXTRA_MODULES_PATH=~/opencv_contrib/modules \
# 	-D BUILD_EXAMPLES=ON ..

make -j4
make clean
make

sudo make install
sudo ldconfig

python -c "import cv2; print cv2.__version__"