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A distutils build extension for PyQt{4,5} applications

Project description

A distutils build extension for PyQt{4,5} applications

Build UI specific elements in tree, controlled by configuration variables in setup.cfg. Running the tool chain is delegated to a couple of internal build commands.

Following layout is assumed:

  i18n/               # keep all translation specific files here
  i18n/    # translation project file (generated, optionally)
  ui/                 # all designer forms, may contain sub folders
  project.qrc         # project resource definition (generated)       # project resources (generated)              # distutils/setuptools module for the project
setup.cfg             # setup configuration


Proper translation is subject of fetching the translatable strings from all forms and source modules, translate them (with linguist), and convert the textual representation (.ts) into binary form (.qm), palatable for QTranslator instances.

There are two ways to accomplish this task: using an intermediate project file (.pro), that can be generated with the built-in command gentrpro, or feeding globbing args to the tools pylupdate and lrelease directly. Unfortunately, the latter way is hampered by some bugs. Hence, the preferred way is using the .pro file.

Because the translation source files (.ts) references forms and sources with relative paths, and the tools pylupdate and lrelease operate relative to the .pro file location, and we want to keep all translation specific files in one place, we run the translation tool chain relative to i18n/.

A new language

  • create an appropriately named file in i18n/ e.g. touch i18n/project_lang.ts

  • build initial translation source with build_ui

  • set up language parameter with linguist once e.g. linguist i18n/project_lang.ts

Translation relies on tr() and translate() used properly in the source.


ui/ and sub folders contain all designer forms. You shouldn’t mix source code and forms in one folder, because forms are translated to Python source files, that you want to handle differently (e.g. exclude from translation, because the translation source is generated from the forms already.

The <form>.ui file is translated to ui_<form>.py. Usually, it contains a single form, where the toplevel object is the camel cased name of the module. E.g.: form.ui contains a widget Form, that is imported from toplevel modules with:

from ui.ui_form import Ui_Form

Typically, this form is subclassed with multiple inheritance:

class Form(QWidget, Ui_Form):
    def __init__(self, parent = None):
        super(Form, self).__init__(parent)


Resource collection files (.qrc) defines resources, that are included within a single module. Typically, this includes images, translation files (.qm), and other static data. These resources are accessed with:


Note the “:” prefix. The resource file is typically included early in the main module:

import project_rc # __IGNORE_WARNING__ (this is not referenced any further)

and the included resources are available in all modules.

distutils_ui contains a built-in command genqrc, that generates .qrc files from globbing patterns. genqrc supports two specific options: prefix and strip. Prefix allows to place all resources under a custom prefix, while strip removes the path from objects. Strip requires, that all files are uniquely named, otherwise some objects are not accessible. The command pyrcc generates the resource module from project.qrc.


The gentrpro and genqrc commands are built-in, therefore they don’t define their own command, rather than process input and output files directly. All other commands call external tools, that must be available and specified with a command parameter in setup.cfg.

Command parameter use {macro} expressions, that references other parameters in the same section, such as {infiles} and {outfiles}, as well as metadata parameter, like {name} and {version}. These parameters can be mixed with file globbing patterns.

infiles and outfiles parameter define input files and targets.

An exclude parameter removes matching elements from infiles.

The chdir parameter allow to change the execution path of that command, also subject to metadata macro expansion.

A special command mode is provided: singlefile. It is used to call the command one by one for every input file. In this mode, additional macros are available, that can be used to further control the output file: {path}, {filename}, and {fileext}. Check the template for pyuic and pyrcc commands for examples.

If you only want to work with a command subset: just define commands in [build_ui] section accordingly.

from import build
from build_ui import build_ui


cmdclass = {
    'build_ui': build_ui,

# Optional: inject ui specific build into standard build process
build.sub_commands.insert(0, ('build_ui', None))


    name = name,
    version = version,
    cmdclass = cmdclass

setup.cfg of build_ui template for PyQt5:

# control the tool chain (default: run all commands)
#commands = gentrpro, pylupdate, lrelease, pyuic, genqrc, pyrcc

# pro files are processed relative to their location, cope with it:
# generate pro file with relative paths from i18n, and call
# pylupdate and lrelease from within i18n
chdir = {name}/i18n
infiles = ../ui/*.ui ../*.py *.ts
outfiles = {name}.pro
exclude = ../{name}

# update translation source files (*.ts) from forms and source files
# -noobsolete will remove all outdated translations
chdir = {name}/i18n
command = pylupdate5 -verbose {infiles}
infiles = {name}.pro
outfiles = {name}_*.ts

# convert translation source files into binary representation (*.qm)
chdir = {name}/i18n
command = lrelease-qt5 {infiles}
infiles = {name}.pro
outfiles = {name}_*.qm

# generate python source files from UI definitions (*.ui)
command = pyuic5 -x -o {outfiles} {infiles}
infiles = {name}/ui/*.ui
outfiles = {name}/ui/ui_{filename}.py
singlefile = true

# generate a resource description file (*.qrc)
chdir = {name}
infiles = images/*.png i18n/*.qm
outfiles = {name}.qrc
# these are specific for genqrc
strip = false
prefix =

# generate a resource module from qrc file
command = pyrcc5 -o {outfiles} {infiles}
infiles = {name}/{name}.qrc
outfiles = {name}/{name}
singlefile = true

The plain UI build is triggered with:

python3 build_ui [-f|--force]

A cleanup of the generated files can be done in a similar fashion:

python3 build_ui [-C|--clean]


  • avoid spaces in filenames

  • ‘.pro’ file approach results in spurious builds


python3 -v build_ui


  1. 2016 Hans-Peter Jansen <>


MIT, Copyright (c) 2016, Hans-Peter Jansen, see LICENSE.txt

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