Semver¶

PEP 440 version parser and comparator -- zero dependencies, stdlib only, Python 3.10+.

Replaces: packaging (Version), semver

Overview¶

The Semver module provides PEP 440 version parsing, normalisation, and comparison using only the Python standard library. It is a drop-in replacement for the core functionality of packaging.version.

File	Description	Dependencies
`semver.py`	Pure Python implementation	None (stdlib only: `re`, `functools`)

How to Use in Your Project¶

Just copy the single .py file into your project:

cp semver/semver.py your_project/

Then import directly:

from semver import Version, version_parse, InvalidVersion

Usage Examples¶

Parsing Versions¶

from semver import Version, version_parse

v = Version("1.2.3")
v = version_parse("1.2.3")  # equivalent convenience function

Comparing Versions¶

from semver import Version

assert Version("2.0") > Version("1.0")
assert Version("1.0a1") < Version("1.0")
assert Version("1.0") == Version("1.0.0")
assert Version("1.0") <= Version("2.0")

Sorting and Selecting¶

from semver import Version

versions = [Version("3.0"), Version("1.0"), Version("2.0b1"), Version("2.0")]
print(sorted(versions))
# [<Version('1.0')>, <Version('2.0b1')>, <Version('2.0')>, <Version('3.0')>]

print(max(versions))
# <Version('3.0')>

Pre-release and Dev Detection¶

from semver import Version

v = Version("1.0a1")
print(v.is_prerelease)  # True
print(v.is_devrelease)  # False

v = Version("1.0.dev3")
print(v.is_prerelease)  # True (dev releases are also pre-releases)
print(v.is_devrelease)  # True

Version Properties¶

from semver import Version

v = Version("2!1.2.3a1.post2.dev3+local.1")
print(v.epoch)         # 2
print(v.release)       # (1, 2, 3)
print(v.major)         # 1
print(v.minor)         # 2
print(v.micro)         # 3
print(v.pre)           # ('a', 1)
print(v.post)          # 2
print(v.dev)           # 3
print(v.local)         # 'local.1'
print(v.base_version)  # '2!1.2.3'
print(v.public)        # '2!1.2.3a1.post2.dev3'

String Normalisation¶

from semver import Version

print(str(Version("1.0alpha1")))   # '1.0a1'
print(str(Version("1.0beta2")))    # '1.0b2'
print(str(Version("1.0preview1"))) # '1.0rc1'
print(str(Version("v1.0")))        # '1.0'
print(str(Version("1.0-1")))       # '1.0.post1'

Error Handling¶

from semver import Version, InvalidVersion

try:
    Version("not a version")
except InvalidVersion as e:
    print(e)  # Invalid version: 'not a version'

PEP 440 Ordering¶

The module implements the full PEP 440 version ordering:

.devN < aN (alpha) < bN (beta) < rcN < release < .postN

Example:

from semver import Version

chain = [
    Version("1.0.dev0"),
    Version("1.0a1"),
    Version("1.0b1"),
    Version("1.0rc1"),
    Version("1.0"),
    Version("1.0.post1"),
]
assert chain == sorted(chain)  # already in order

API Reference¶

`Version(version: str)`¶

Parse a PEP 440 version string.

Raises: InvalidVersion if the string does not conform to PEP 440.

Properties:

Property	Type	Description
`epoch`	`int`	Epoch segment (`0` when absent)
`release`	`tuple[int, ...]`	Release segment as integers
`pre`	`tuple[str, int] \\| None`	Pre-release tag, e.g. `('a', 1)`
`post`	`int \\| None`	Post-release number
`dev`	`int \\| None`	Dev-release number
`local`	`str \\| None`	Local version label
`major`	`int`	First release component
`minor`	`int`	Second release component (`0` if absent)
`micro`	`int`	Third release component (`0` if absent)
`base_version`	`str`	Version without pre/post/dev/local
`public`	`str`	Version without local segment
`is_prerelease`	`bool`	`True` if pre-release or dev-release
`is_devrelease`	`bool`	`True` if dev-release
`is_postrelease`	`bool`	`True` if post-release

Operators: ==, !=, <, >, <=, >=, hash(), str(), repr()

`version_parse(version: str) -> Version`¶

Convenience function equivalent to Version(version).

`InvalidVersion`¶

Exception raised for unparseable version strings. Subclass of ValueError.

Comparison with packaging¶

Feature	zerodep semver	packaging
Dependencies	None (stdlib only)	None (but adds a pip dependency)
API	`Version("1.0")`	`Version("1.0")`
Comparison	All operators	All operators
Properties	`is_prerelease`, `is_devrelease`, etc.	Same
Normalisation	Full PEP 440	Full PEP 440
Performance	Comparable (see benchmark)	Comparable
Implementation	Single file (~300 lines)	Package

When to use zerodep: You want zero pip dependencies and only need PEP 440 version parsing/comparison.

When to use packaging: You need the full packaging library (specifiers, requirements, markers, tags).

Benchmark¶

Benchmarked against packaging across parsing, sorting, comparison, and property access.

See Semver Benchmark for detailed results.