depsolver is a package dependency solver in python.

Examples:

# Simple scenario: nothing installed, install numpy, 2 versions available
# in the repository
from depsolver import PackageInfo, Pool, Repository, Request, Requirement, Solver

numpy_1_6_1 = PackageInfo.from_string("numpy-1.6.1")
numpy_1_7_0 = PackageInfo.from_string("numpy-1.7.0")

repo = Repository([numpy_1_6_1, numpy_1_7_0])
installed_repo = Repository()
pool = Pool([repo, installed_repo])

# only one operation here: install numpy (most recent available version
# automatically picked up)
request = Request(pool)
request.install(Requirement.from_string("numpy"))
for operation in Solver(pool, installed_repo).solve(request):
    print operation

A more complex scenario which currently fails with pip (pypa/pip#174):

#  - A requires B and C
#  - B requires D <= 1.1
#  - C requires D <= 0.9

a_1_0_0 = PackageInfo.from_string("A-1.0.0; depends (B, C)")
b_1_0_0 = PackageInfo.from_string("B-1.0.0; depends (D <= 1.1.0)")
c_1_0_0 = PackageInfo.from_string("C-1.0.0; depends (D <= 0.9.0)")
d_1_1_0 = PackageInfo.from_string("D-1.1.0")
d_0_9_0 = PackageInfo.from_string("D-0.9.0")

repo = Repository([a_1_0_0, b_1_0_0, c_1_0_0, d_1_1_0, d_0_9_0])
installed_repo = Repository()
pool = Pool([repo, installed_repo])

# despolver resolves each dependency 'globally', and does not install
# D-1.1.0 as pip currently does
request = Request(pool)
request.install(Requirement.from_string("A"))
for operation in Solver(pool, installed_repo).solve(request):
    print operation

Its main features:

• pure python. Both >= 2.5 and >= 3.2 are supported from a single codebase.
• only depends on the six library
• use SAT solver to solve dependencies
• handle dependencies, provides, conflict and replaces
• supports multiple version formats (semver semantic versions RFC and debian formats currently supported)
• reasonably well tested (> 90 % coverage)

It is still experimental, and subject to arbitrary changes.

The design is strongly inspired from PHP Composer packager, itself started as a port of libsolver.

Thanks to Enthought to let me open source this project !

Note:

The work on depsolver is temporarily handed over to the enstaller project (in enstaller.new_solver), to ease the integration with our needs at Enthought. Once the implementation will be finished, we will extract back the solver into depsolver. We expect a fully functional solver for end of Q1 2015.