`auto` will auto-detect platform using environment variables, such as `TRAVIS_OS_NAME`/`APPVEYOR`/`CIRCLECI`.
For `linux` you need Docker running, on Mac or Linux. For `macos`, you need a Mac machine, and note that this script is going to automatically install MacPython on your system, so don't run on your development machine. For `windows`, you need to run in Windows, and it will build and test for all versions of Python at `C:\PythonXX[-x64]`.
Space-separated list of builds to build and skip. Each build has an identifier like `cp27-manylinux1_x86_64` or `cp34-macosx_10_6_intel` - you can list specific ones to build and `cibuildwheel` will only build those, and/or list ones to skip and `cibuildwheel` won't try to build them.
When both options are specified, both conditions are applied and only builds with a tag that matches `CIBW_BUILD` and does not match `CIBW_SKIP` will be built.
The format is `python_tag-platform_tag`. The tags are as defined in [PEP 0425](https://www.python.org/dev/peps/pep-0425/#details).
Python tags look like `cp27``cp34``cp35``cp36``cp37`
Platform tags look like `macosx_10_6_intel``manylinux1_x86_64``manylinux1_i686``win32``win_amd64`
You can also use shell-style globbing syntax (as per `fnmatch`)
Examples:
- Only build on Python 3.6: `CIBW_BUILD=cp36-*`
- Skip building on Python 2.7 on the Mac: `CIBW_SKIP=cp27-macosx_10_6_intel`
- Skip building on Python 2.7 on all platforms: `CIBW_SKIP=cp27-*`
- Skip Python 2.7 on Windows: `CIBW_SKIP=cp27-win*`
- Skip Python 2.7 on 32-bit Windows: `CIBW_SKIP=cp27-win32`
- Skip Python 3.4 and Python 3.5: `CIBW_SKIP=cp34-* cp35-*`
- Skip Python 3.6 on Linux: `CIBW_SKIP=cp36-manylinux*`
- Only build on Python 3 and skip 32-bit builds: `CIBW_BUILD=cp3?-*` and `CIBW_SKIP=*-win32 *-manylinux1_i686`
In addition to the above, `cibuildwheel` always defines the environment variable `CIBUILDWHEEL=1`. This can be useful for [building wheels with optional extensions](https://github.com/joerick/cibuildwheel/wiki/Building-packages-with-optional-C-extensions).
A shell command to run before building the wheel. This option allows you to run a command in **each** Python environment before the `pip wheel` command. This is useful if you need to set up some dependency so it's available during the build.
If dependencies are required to build your wheel (for example if you include a header from a Python module), set this to `pip install .`, and the dependencies will be installed automatically by pip. However, this means your package will be built twice - if your package takes a long time to build, you might wish to manually list the dependencies here instead.
The active Python binary can be accessed using `python`, and pip with `pip`; `cibuildwheel` makes sure the right version of Python and pip will be executed. `{project}` can be used as a placeholder for the absolute path to the project's root.
An alternative docker image to be used for building [`manylinux1`](https://github.com/pypa/manylinux) wheels. `cibuildwheel` will then pull these instead of the official images, [`quay.io/pypa/manylinux1_x86_64`](https://quay.io/pypa/manylinux1_i686) and [`quay.io/pypa/manylinux1_i686`](https://quay.io/pypa/manylinux1_i686).
Beware to specify a valid docker image that can be used the same as the official, default docker images: all necessary Python and pip versions need to be present in `/opt/python/`, and the `auditwheel` tool needs to be present for `cibuildwheel` to work. Apart from that, the architecture and relevant shared system libraries need to be manylinux1-compatible in order to produce valid `manylinux1` wheels (see https://github.com/pypa/manylinux and [PEP 513](https://www.python.org/dev/peps/pep-0513/) for more details).
Shell command to run tests after the build. The wheel will be installed automatically and available for import from the tests. `{project}` can be used as a placeholder for the absolute path to the project's root and will be replaced by `cibuildwheel`.
On Linux and Mac, the command runs in a shell, so you can write things like `cmd1 && cmd2`.
An number from 1 to 3 to increase the level of verbosity (corresponding to invoking pip with `-v`, `-vv`, and `-vvv`), between -1 and -3 (`-q`, `-qq`, and `-qqq`), or just 0 (default verbosity). These flags are useful while debugging a build when the output of the actual build invoked by `pip wheel` is required.