Python Packages¶
“Python is known for it’s ‘batteries included’ philosophy and has a rich standard library. However, being a popular language, the number of third party packages is much larger than the number of standard library packages. So it eventually becomes necessary to discover how packages are used, found ...”
PyPI¶
The Python Package Index (PyPI), formerly known as the Cheeseshop, is a central repository containing tens of thousands of ready to install Python community projects and distributions. It will become an integral part of your Python ecosystem.
pip¶
Pip works with PyPI, it’s used to install and manage Python packages. Pip replaces easy_install.
| Action | Command |
|---|---|
| install package | pip install <pkg-name> |
| uninstall package | pip uninstall <pkg-name> |
| upgrade package | pip install -U <pkg-name> |
Pip was installed as part of Python, but now we need to upgrade it to make sure we are using the latest version:
pip install --upgrade pip
| Command | Action |
|---|---|
| pip list | List all packages installed in the current environment. |
| pip search <text> | List all PyPI packages whose name or summary contains <text>. |
| pip show <pkg-name> ... | Show information about one or more installed packages. |
Go head and practice:
pip list
pip search web2py
pip show pip
Wheels¶
A Wheel is python distribution standard that doesn’t require building or complation; wheels replace eggs . Wheel has an official PEP; Egg doesn’t.
Use Wheel if you try to install a package from PyPI and you see this ...
Warning
error: Unable to find vcvarsall.bat
The package is probably a C extension and it can’t find a compiler in Windows. The easiest way to install these types of packages is to download the Wheel file from the Unofficial Windows Binaries for Python Extension Packages.
For example, locate the pandas, a data analysis package. The Wheel files look something like this:
pandas-0.18.1-cp27-cp27m-win32.whl
The Wheel file format is is defined in PEP 425 as:
{distribution}-{version}(-{build tag})?-{python tag}-{abi tag}-{platform tag}.whl
“When people speak of Python they often mean not just the language but also the CPython implementation. Python is actually a specification for a language that can be implemented in many different ways.”
| File Name | Package-Version | Python-Version | 32/64-bit? |
|---|---|---|---|
| pandas-0.18.1-cp27-cp27m-win32.whl | 0.18.1 | Python 2.7 | 32-bit |
| pandas-0.18.1-cp27-cp27m-win_amd64.whl | 0.18.1 | Python 2.7 | 64-bit |
| pandas-0.18.1-cp35-cp35m-win32.whl | 0.18.1 | Python 3.5 | 32-bit |
| pandas-0.18.1-cp35-cp35m-win_amd64.whl | 0.18.1 | Python 3.5 | 64-bit |
Once you download the correct Wheel file for your Python version & architecture you can install it with pip:
pip install <wheel-filename>
Make sure to include the path when you specify the Wheel file, for example:
pip install c:\users\<username>\downloads\pandas-0.18.1-cp27-cp27m-win32.whl