Long time user of Python here and recent user of Mathematica.
Some observations I have are that they're both great. Python is a nice open source scripting language, but getting libraries to work can sometimes be a pain. Mathematica is basically install this and everything is included. The Mathematica documentation is amazing and it is really simple how to do most things. The whole iPhone "there is an app for that" is equivalent to "there is a function for that".
Graph Theory works flawlessly in Mathematica. In Python, there is a module to Graphviz. Let me know if Python has something new though. There are a lot of other examples. Mathematica's Import[] function can read over 150 different file types including: CSV,.XLS, genetic encoding files, optimization files....whatever. It is usually far easier and more consistent than finding a corresponding Python library and struggling with the install and minimal documentation. Let me be clear that Python is awesome and rocks and i think Jupyter is moving it in the right direction. I just feel like many dismiss Mathematica as something that does Calculus homework rather than what it is today which is a massive 20 million LOC conglomeration of C & Java & Wolfram language that does everything from Statistics, Machine Learning, Visualization, BlockChain, 3D printing, NodeGraphs, data sets and analysis...etc in a single consistent package. It is expensive and proprietary and certainly has its own faults, but a lot of that cash is funneled back into a great product.