If you already have Anaconda or Miniconda installed, you can install the latest version with conda:
conda install sympy
Another way of installing SymPy is using pip:
pip install sympy
Note that this might require root privileges, so one might acually need
sudo pip install sympy
Most linux distributions also offer SymPy in their package repositories. For Fedora one would install SymPy with
sudo dnf install python-sympy sudo dnf install python3-sympy
The first one installs the python 2 version of the package, the latter python 3.
On OpenSuse the respective commands are:
sudo zypper install python-sympy sudo zypper install python3-sympy
The packages for OpenSuse 42.2 seem rather outdated, so one of the first methods should be prefered.