API stability

From its first release, cryptography has had a strong API stability policy.

What does this policy cover?

This policy includes any API or behavior that is documented in this documentation.

What does “stable” mean?

  • Public APIs will not be removed or renamed without providing a compatibility alias.

  • The behavior of existing APIs will not change.

What doesn’t this policy cover?

  • We may add new features, things like the result of dir(obj)) or the contents of obj.__dict__ may change.

  • Objects are not guaranteed to be pickleable, and pickled objects from one version of cryptography may not be loadable in future versions.

  • Development versions of cryptography. Before a feature is in a release, it is not covered by this policy and may change.

Security

One exception to our API stability policy is for security. We will violate this policy as necessary in order to resolve a security issue or harden cryptography against a possible attack.

Versioning

This project uses a custom versioning scheme as described below.

Given a version cryptography X.Y.Z,

  • X.Y is a decimal number that is incremented for potentially-backwards-incompatible releases.

    • This increases like a standard decimal. In other words, 0.9 is the ninth release, and 1.0 is the tenth (not 0.10). The dividing decimal point can effectively be ignored.

  • Z is an integer that is incremented for backward-compatible releases.

Deprecation

From time to time we will want to change the behavior of an API or remove it entirely. In that case, here’s how the process will work:

  • In cryptography X.Y the feature exists.

  • In cryptography X.Y + 0.1 using that feature will emit a UserWarning.

  • In cryptography X.Y + 0.2 using that feature will emit a UserWarning.

  • In cryptography X.Y + 0.3 the feature will be removed or changed.

In short, code that runs without warnings will always continue to work for a period of two releases.

From time to time, we may decide to deprecate an API that is particularly widely used. In these cases, we may decide to provide an extended deprecation period, at our discretion.