install_python.sh

#!/usr/bin/env bash

# Compiles and installs a custom Python dev environment
# separate from the rest of the packages on a CentOS7 
# system only.

# This script needs to be run as root and must have
# public internet access to grab the Python tarball.

# This isn't meant to work on anything other than CentOS7
# and will probably even break across major versions.

PYTHON_VERSION="3.7.2"
PYTHON_BINARY="python3.7"
PIP_BINARY="pip3.7"
OFFICIAL_MD5="02a75015f7cd845e27b85192bb0ca4cb"
TEMP_DIR="/tmp/python-${PYTHON_VERSION}-scripted-install"

# Install pre-requisite tools
echo "========INSTALLING PREREQUISITE PACKAGES========="
yum -y update
yum -y groupinstall "development tools"
# These are needed for compilation of all Python features.
yum -y install zlib-devel bzip2-devel \
    openssl-devel ncurses-devel \
    sqlite-devel readline-devel \
    tk-devel gdbm-devel db4-devel \
    libpcap-devel xz-devel expat-devel \
    libffi-devel
# Make sure we can download Python
yum -y install wget

echo "========DOWNLOADING PYTHON ${PYTHON_VERSION}========="
mkdir -p ${TEMP_DIR}; cd ${TEMP_DIR}
wget https://www.python.org/ftp/python/${PYTHON_VERSION}/Python-${PYTHON_VERSION}.tgz
md5=$(md5sum Python-${PYTHON_VERSION}.tgz |awk '{print $1}')
if [[ "${OFFICIAL_MD5}" -ne "${md5}" ]]; then
    echo "ERROR: MD5 mismatch!"
    echo "Expected MD5: ${OFFICIAL_MD5}"
    echo "Actual MD5: ${md5}"
    exit 1
fi

echo "========INSTALLING PYTHON ${PYTHON_VERSION}========="
tar xf Python-${PYTHON_VERSION}.tgz
cd Python-${PYTHON_VERSION}
echo "Compliling with shared libraries into /usr/local/lib"
./configure --prefix=/usr/local --enable-shared LDFLAGS="-Wl,-rpath /usr/local/lib"
make && make altinstall

echo "========INSTALLING PIP, SETUPTOOLS, AND WHEEL========="
wget https://bootstrap.pypa.io/get-pip.py
python3.7 get-pip.py

# echo "========DEFAULTING TO NEW PYTHON========="
# alternatives --install /usr/bin/python python /usr/bin/python2 50
# alternatives --install /usr/bin/python python /usr/local/bin/${PYTHON_BINARY} 100
# alternatives --install /usr/bin/pip pip /usr/local/bin/${PIP_BINARY} 50

# echo "========UPDATING PIP========="
# CentOS 6/7 has an annoying feature where /usr/local/bin is hardcoded into the bash
# binary $PATH BEFORE /usr/bin, and /bin, meaning that the exising /usr/local/bin/pip
# will take precedence in the PATH before /usr/bin/pip, rendering alternatives moot.
# To work around this, I just rename the binary for the old pip, which of course will
# break that RPM.
# mv /usr/local/bin/pip /usr/local/bin/pip.old
# /usr/local/bin/${PIP_BINARY} install --upgrade pip

echo "========UPDATING SHARED LIBS========="
echo "/usr/local/lib/" >> /etc/ld.so.conf
ldconfig

echo "========CONFIGURING VIRTUAL ENVIRONMENTS========="
sudo /usr/local/bin/${PYTHON_BINARY} install virtualenv
/usr/local/bin/virtualenv /usr/local/venv/default
source /usr/local/venv/default/bin/activate
pip install powerline-status

echo "========INSTALL COMPLETE========="
echo "To remove temporary files: rm -rf ${TEMP_DIR}"