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Makes it easy to work with Python projects containing lots of packages, of which you only want to develop some.

Project description

mxdev [mɪks dɛv] is a utility that makes it easy to work with Python projects containing lots of packages, of which you only want to develop some.

It builds on top of the idea to have stable version constraints and then develop from a VCS on top of it.

As part of above use-case sometimes versions of the stable constraints need an override with a different (i.e. newer) version.

Other software following the same idea are mr.developer for Python’s zc.buildout or mrs-developer for NPM packages.

mxdev 2.0 needs pip version 22 at minimum to work properly


mxdev procedure is:

  1. Configuration is read,

  2. Requirements and constraints (given in configuration) are read.

  3. Sources from VCS are fetched into a target directory,

  4. Modified constraints (handled packages commented, overridden versions replaced) and requirements (handled packages as editable from sources) are written.

mxdev will not run pip for you!


Given a requirements.txt (or similar named) file which itself references a constraints.txt file inside.

Create an INI file, like sources.ini in configparser.ExtendedInterpolation syntax.

Main section [settings]

The main section must be called [settings], even if kept empty. In the main sections the input and output files are defined.


Main requirements file to start with. This can be an URL too.

If given an empty value mxdev will only generate output from the information given in INI file itself.

Default: requirements.txt


Output of the combined requirements including development sources to be used later with pip install. Default: requirements-mxdev.txt


Output of the combined constraints. Default: constraints-mxdev.txt


Target directory for sources from VCS. Default: ./sources


Default for install-mode on section, read there for details Allowed values: direct or skip Default: direct


Override package versions which already defined in a dependent constraints file. I.e. an upstream constraints.txt contains already somefancypackage==2.0.3. Given, for some reason (like with my further developed sources), we need version 3.0.0 of above package. Then in this section this can be defined as:

version-overrides =

It is possible to add as many overrides as needed. When writing the constraints-out, the new version will be taken into account. If there is a source-section defined for the same package, the source will be used and entries here are ignored.


Ignore packages which are already defined in a dependent constraints file. No new version will be provided. This is specifically handy if a package is going to be installed editable from local file system (like -e .), but was already pinned in an upstream constraints-file.

This can be defined as:

ignores =

Additional, custom variables can be defined as key = value pair. Those can be referenced in other values as ${settings:key} and will be expanded there.

Subsequent package source sections

All other sections are defining the sources to be used.


The section name is the package name.

url = URL

the URL to the source in VCS and must follow the pip install editable format.

Attention, this differs from the format one copies from Github/Gitlab, etc. For convienince mxdev applies auto-correction for this common cases:

  • ssh:// -> git+ssh://

  • git@ -> git+ssh://git@

  • https:// -> git+https://

The URL is required.


the branch name or tag to checkout. Defaults to main.

extras = EXTRA1,EXTRA2

Package extras to install. Default empty.

subdirectory = SUBPATH

For specifying the path to the Python package, when it is not in the root of the VCS directory. Default empty.


Target directory for source from this section. Default to default target directory configured in main section [settings] default-target = value.


There are different modes of pip installation:


Do not install with pip, just clone/update the repository.


Install the package using pip -e PACKAGEPATH. Dependencies are resolved immediately.

Defaults to default mode configured in main section [settings] default-install-mode = value.


Run mxdev -c sources.ini.

Now, use the generated requirements and constraints files with i.e. pip install -r requirements-mxdev.txt.

For more options run mxdev --help.

Example Configuration

Example sources.ini

This looks like so:

requirements-in = requirements.txt
requirements-out = requirements-mxdev.txt
contraints-out = constraints-mxdev.txt

version-overrides =
    baz.baaz = 1.9.32

ignores =

# custom variables
github = git+ssh://
mygit = git+ssh://

url = ${settings:github}orga/
branch = fix99
extras = test,baz

url = ${settings:mygit}customers/fancycorp/kup.fancyproject.git
branch = fix99
extras = test,baz

Examples at GitHub



There is a constraint file like -c constraints.txt with a package with a version pin. Then it is not possible to install this package in a requirements file editable like -r requirements.txt with -e git+ssh:// Neither it is possible to override inherited version constraints with custom ones.


A pre-processor fetches (as this can be an URL) and expands all -c SOMEOTHER_FILE_OR_URL and -r SOMEOTHER_FILE_OR_URL files into one, filtering out all packages given in a configuration file. For each of those packages a -e ... entry is generated instead and written to a new TARGET.txt. Same is true for version overrides: a new entry is written to the resulting constraints file while the original version is disabled. The configuration is read from a file sources.ini in ExtendedInterpolation INI syntax (YAML would be nice, but the package must have as less dependencies as possible to other packages).


Mx (generally pronounced like mix [mɪks], or [məks] in the UK) is meant to be a gender-neutral alternative to the titles Mr. and Ms. but also associates with mix.


2.0.0 (2022-01-31)

  • Depend on pip 22, where interdependency mode is no longer needed. Remove all interdependency related code. [jensens]

  • Better error message if the requirements-in file does not exists. [jensens]

  • Better last message with the full pip command. [jensens]

  • Allow empty requirements-in configuration. [jensens]

1.1.0 (2021-12-29)

  • Feature: Ignore existing constraints. New setting ignores with a list of packages (one per line) to ignore from constraints without providing a version. [jensens]

1.0.1 (2021-12-21)

  • Fix: If a developed package depends on another developed package the dependent package was ignored sometimes (!?). Instead the last release was taken. Solution: Install it with the –pre option in order allow the other non-final/in-development release. [jensens]

1.0.0 (2021-12-12)

  • Defaults for “outfiles” are *-mxdev.txt now. [jensens]

1.0.0b4 (2021-12-07)

  • Fix interdependency mode. [jensens]

1.0.0b3 (2021-12-07)

  • Fix: Do not apply override disabling on requirements. [jensens]

1.0.0b2 (2021-12-07)

  • Add feature: version overrides. [jensens]

1.0.0b1 (2021-12-04)

  • Add -s or --silent option. [jensens]

  • Beautified output. [jensens]

  • Fixed missing CR if *.txt does not end with newline. [jensens]

1.0.0a9 (2021-12-01)

  • Added auto correction for pip URLs, so that GitHub or Gitlab URLs can be used as copied in sources.ini. [zworkb]

1.0.0a8 (2021-11-30)

  • Added interdependency handling to avoid manual dependency order resolution. [jensens, gogobd]

  • Added skip mode to exclude packages from installation (clone/update only). [jensens, gogobd]

  • Removed position feature. [jensens, gogobd]

1.0.0a7 (2021-11-30)

  • Removed Workaround for libvcs and depend on libvcs>=0.10.1. [jensens]

1.0.0a6 (2021-11-30)

1.0.0a5 (2021-11-30)

1.0.0a4 (2021-11-29)

  • Fix: editable can be configured to be processed before or after initial requirements. [jensens]

1.0.0a3 (2021-11-23)

  • Fix #1: Re-run of pip vanishes committed changes [jensens]

1.0.0a2 (2021-11-21)

  • Fix/simplify packaging. [jensens]

  • Implement subdirectory editable install [jensens]

  • Implement package extras [jensens]

1.0.0a1 (2021-11-21)

  • Initial work. [jensens]

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