Freezing Applications with oxidized_importer

oxidized_importer can be used to create and run frozen Python applications, where Python resources data (module source and bytecode, etc) is frozen/packaged and distributed next to your application.

This is conceptually similar to what PyOxidizer does. The major difference is that PyOxidizer will package and distribute a Python distribution with your application: when only oxidized_importer is being used, the Python distribution is provided by some other means (it is typically already installed on the system). This makes oxidized_importer a light-weight alternative to PyOxidizer for scenarios where PyOxidizer isn’t suitable or viable.

High-Level Freezing Workflow

The steps for freezing an application all look the same:

  1. Load OxidizedResource instances into an OxidizedFinder instance so they are indexed.

  2. Serialize indexed resources.

  3. Write the serialized resources blob somewhere along with any files (if using filesystem-based loading).

  4. Somehow make that resources blob available to others (you could add it as a resource file in your Python package for example).

  5. From your application, construct an OxidizedFinder instance and load the resources blob you generated.

  6. Register the OxidizedFinder instance as the first element on sys.meta_path.

The next sections show what this may look like.

Indexing and Serializing Resources

In your build process, you’ll need to index resources and serialize them. You can construct OxidizedResource instances directly and hand them off to an OxidizedFinder instance. But you’ll probably want to use OxidizedResourceCollector to make this simpler.

Try something like the following:

import os
import stat
import sys

import oxidized_importer

# Create a collector to help with managing resources.
collector = oxidized_importer.OxidizedResourceCollector(

# Add all known Python resources by scanning sys.path.
# Note: this will pull in the Python standard library and
# any other installed packages, which may not be desirable!
for path in sys.path:
    # Only directories can be scanned by oxidized_importer.
    if os.path.isdir(path):
        for resource in oxidized_importer.find_resources_in_path(path):

# Turn the collected resources into ``OxidizedResource`` and file
# install rules.
resources, file_installs = collector.oxidize()

# Now index the resources so we can serialize them.
finder = oxidized_importer.OxidizedFinder()

# Turn the indexed resources into an opaque blob.
packed_data = finder.serialize_indexed_resources()

# Write out that data somewhere.
with open("oxidized_resources", "wb") as fh:

# Then for all the file installs, materialize those files.
for (path, data, executable) in file_installs:
    path.parent.mkdir(parents=True, exist_ok=True)

    with"wb") as fh:

    if executable:
        path.chmod(path.stat().st_mode | stat.S_IEXEC)

At this point, you’ve collected all known Python resources and written out a data structure describing them all. For resources targeting in-memory loading, the content of those resources is embedded in the data structure. For resources targeting filesystem-relative loading, the data structure contains the relative path to those resources. And you’ve written out the files in the locations where those relative paths point to.

Loading Serialized Resources in Your Application

Now, from our application code, we need to load the resources and register the custom importer with Python:

import os
import sys

import oxidized_importer

# Load those resources into an instance of our custom importer. This
# will read the index in the passed data structure and make all
# resources immediately available for importing.
finder = oxidized_importer.OxidizedFinder()

# If the relative path of filesystem-based resources is not relative
# to the current executable (which is likely the ``python3`` executable),
# you'll need to set ``origin`` to the directory the resources are
# relative to.
finder = oxidized_importer.OxidizedFinder(

# Register the meta path finder as the first item, making it the
# first finder that is consulted.
sys.meta_path.insert(0, finder)

# At this point, you should be able to ``import`` modules defined
# in the resources data!