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Build Configuration#

pdm uses the PEP 517 to build the package. A build backend is what drives the build system to build source distributions and wheels from arbitrary source trees.

pdm also ships with its own build backend, pdm-pep517. Besides the PEP 621 project meta, it reads additional configurations stored in [tool.pdm.build] table to control the build behavior. To use it, include the following in your pyproject.toml(It will be done automatically if you use the pdm init or pdm import to create the file):

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[build-system]
requires = ["pdm-pep517"]
build-backend = "pdm.pep517.api"

Note

The following part of this documentation assumes you are using the pdm-pep517 backend as mentioned above. Different backends will have different configurations.

Dynamic versioning#

pdm-pep517 supports dynamic versions from two sources. To enable dynamic versioning, remember to include version in the dynamic field of PEP 621 metadata:

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[project]
...
dynamic = ["version"]

Dynamic version from file#

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[tool.pdm]
version = { source = "file", path = "mypackage/__version__.py" }

The backend will search for the pattern __version__ = "{version}" in the given file and use the value as the version.

Tip

Thanks to the TOML syntax, the above example is equivalent to the following:

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[tool.pdm.version]
source = "file"
path = "mypackage/__version__.py"
Or: 
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[tool.pdm]
version.source = "file"
version.path = "mypackage/__version__.py"

Dynamic version from SCM#

If you've used setuptools-scm you will be familiar with this approach. pdm-pep517 can also read the version from the tag of your SCM repository:

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[tool.pdm]
version = { source = "scm" }

Specify the version manually#

When building the package, pdm-pep517 will require the SCM to be available to populate the version. If that is not the case, you can still specify the version with an environment variable PDM_PEP517_SCM_VERSION:

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export PDM_PEP517_SCM_VERSION="1.2.3"
pdm build

Write the version to file#

For dynamic version read from SCM, it would be helpful to write the evaluated value to a file when building a wheel, so that you do not need importlib.metadata to get the version in code.

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[tool.pdm.version]
source = "scm"
write_to = "mypackage/__version__.py"
write_template = "__version__ = '{}'"  # optional, default to "{}"

For source distributions, the version will be frozen and converted to a static version in the pyproject.toml file, which will be included in the distribution.

Include and exclude files#

To include extra files and/or exclude files from the distribution, give the paths in includes and excludes configuration, as glob patterns:

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[tool.pdm.build]
includes = [
    "**/*.json",
    "mypackage/",
]
excludes = [
    "mypackage/_temp/*"
]

In case you may want some files to be included in source distributions only, use the source-includes field:

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[tool.pdm.build]
includes = [...]
excludes = [...]
source-includes = ["tests/"]

Note that the files defined in source-includes will be excluded automatically from binary distributions.

Default values for includes and excludes#

If you don't specify any of these fields, PDM can determine the values for you to fit the most common workflows, in the following manners:

  • Top-level packages will be included.
  • tests package will be excluded from non-sdist builds.
  • src directory will be detected as the package-dir if it exists.

If your project follows the above conventions you don't need to config any of these fields and it just works. Be aware PDM won't add PEP 420 implicit namespace packages automatically and they should always be specified in includes explicitly.

Select another package directory to look for packages#

Similar to setuptools' package_dir setting, one can specify another package directory, such as src, in pyproject.toml easily:

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[tool.pdm.build]
package-dir = "src"

If no package directory is given, PDM can also recognize src as the package-dir implicitly if:

  1. src/__init__.py doesn't exist, meaning it is not a valid Python package, and
  2. There exist some packages under src/*.

Implicit namespace packages#

As specified in PEP 420, a directory will be recognized as a namespace package if:

  1. <package>/__init__.py doesn't exist, and
  2. There exist normal packages and/or other namespace packages under <package>/*, and
  3. <package> is explicitly listed in includes

Custom file generation#

During the build, you may want to generate other files or download resources from the internet. You can achieve this by the setup-script build configuration:

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[tool.pdm.build]
setup-script = "build.py"

In the build.py script, pdm-pep517 looks for a build function and calls it with two arguments:

  • src: (str) the path to the source directory
  • dst: (str) the path to the distribution directory

Example:

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# build.py
def build(src, dst):
    target_file = os.path.join(dst, "mypackage/myfile.txt")
    os.makedirs(os.path.dirname(target_file), exist_ok=True)
    download_file_to(dst)

The generated file will be copied to the resulted wheel with the same hierarchy, you need to create the parent directories if necessary.

Build Platform-specific Wheels#

setup-script can also be used to build platform-specific wheels, such as C extensions. Currently, building C extensions still relies on setuptools.

Set run-setuptools = true under setup-script, and pdm-pep517 will generate a setup.py with the custom build function in the script then run python setup.py build to build the wheel and any extensions:

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# pyproject.toml
[tool.pdm.build]
setup-script = "build_setuptools.py"
run-setuptools = true

In the setup-script, the expected build function receives the argument dictionary to be passed to the setuptools.setup() call. In the function, you can update the keyword dictionary with any additional or changed values as you want.

Here is an example adapted to build MarkupSafe:

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# build_setuptools.py
from setuptools import Extension

ext_modules = [
    Extension("markupsafe._speedups", ["src/markupsafe/_speedups.c"])
]

def build(setup_kwargs):
    setup_kwargs.update(ext_modules=ext_modules)

If you run pdm build(or any other build frontends such as build), PDM will build a platform-specific wheel file as well as a sdist.

By default, every build is performed in a clean and isolated environment, only build requirements can be seen. If your build has optional requirements that depend on the project environment, you can turn off the environment isolation by pdm build --no-isolation or setting config build_isolation to falsey value.

Override the "Is-Purelib" value#

If this value is not specified, pdm-pep517 will build platform-specific wheels if run-setuptools is true.

Sometimes you may want to build platform-specific wheels but don't have a build script (the binaries may be built or fetched by other tools). In this case you can set the is-purelib value in the pyproject.toml to false:

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[tool.pdm.build]
is-purelib = false

Editable build backend#

PDM implements PEP 660 to build wheels for editable installation. One can choose how to generate the wheel out of the two methods:

  • path: (Default)The legacy method used by setuptools that create .pth files under the packages path.
  • editables: Create proxy modules under the packages path. Since the proxy module is looked for at runtime, it may not work with some static analysis tools.

Read the PEP for the difference of the two methods and how they work.

Specify the method in pyproject.toml like below:

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[tool.pdm.build]
editable-backend = "path"

editables backend is more recommended but there is a known limitation that it can't work with PEP 420 namespace packages. So you would need to change to path in that case.

About Python 2 compatibility

Due to the fact that the build backend for PDM managed projects requires Python>=3.6, you would not be able to install the current project if Python 2 is being used as the host interpreter. You can still install other dependencies not PDM-backed.

Use other PEP 517 backends#

Apart from pdm-pep517, pdm plays well with any PEP 517 build backends that read PEP 621 metadata. At the time of writing, flit(backend: flit-core) and hatch(backend: hatchling) are working well with PEP 621 and setuptools has experimental support. To use one of them, you can specify the backend in the pyproject.toml:

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[build-system]
requires = ["flit_core >=3.2,<4"]
build-backend = "flit_core.buildapi"

PDM will call the correct backend when doing pdm build.