Python's packaging ecosystem
The core of Python's packaging ecosystem is the Python Packaging Index. PyPI is a vast public repository of (mostly) free-to-use Python projects that at the time of writing hosts almost three and a half million distributions of more than 250,000 packages. That's not the biggest number among all package repositories (npm surpassed a million packages in 2019) but it still places Python among the leaders of packaging ecosystems.
Such a large ecosystem of packages doesn't come without a price. Modern applications are often built using multiple packages from PyPI that often have their own dependencies. Those dependencies can also have their own dependencies. In large applications, such dependency chains can go on and on. Add the fact that some packages may require specific versions of other packages and you may quickly run into dependency hell—a situation where it is almost impossible to resolve conflicting version requirements...