# API and ABI Versioning

CPython exposes its version number in the following macros. Note that these correspond to the version code is built with, not necessarily the version used at run time.

See C API Stability for a discussion of API and ABI stability across versions.

PY_MAJOR_VERSION

  The `3` in `3.4.1a2`.

PY_MINOR_VERSION

  The `4` in `3.4.1a2`.

PY_MICRO_VERSION

  The `1` in `3.4.1a2`.

PY_RELEASE_LEVEL

  The `a` in `3.4.1a2`. This can be `0xA` for alpha, `0xB` for beta, `0xC` for release candidate or `0xF` for final.

PY_RELEASE_SERIAL

  The `2` in `3.4.1a2`. Zero for final releases.

PY_VERSION_HEX

  The Python version number encoded in a single integer.

  The underlying version information can be found by treating it as a 32 bit number in the following manner:

  Bytes | Bits (big endian order) | Meaning | Value for `3.4.1a2`
  --- | --- | --- | ---
  1 | 1-8 | `PY_MAJOR_VERSION` | `0x03`
  2 | 9-16 | `PY_MINOR_VERSION` | `0x04`
  3 | 17-24 | `PY_MICRO_VERSION` | `0x01`
  4 | 25-28 | `PY_RELEASE_LEVEL` | `0xA`
  29-32 | `PY_RELEASE_SERIAL` | `0x2`

  Thus `3.4.1a2` is hexversion `0x030401a2` and `3.10.0` is hexversion `0x030a00f0`.

  This version is also available via the symbol `Py_Version`.

const unsigned long Py_Version
  Part of the Stable ABI since version 3.11.

  The Python runtime version number encoded in a single constant integer, with the same format as the `PY_VERSION_HEX` macro. This contains the Python version used at run time.

  New in version 3.11.

All the given macros are defined in Include/patchlevel.h.