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FADES(1) General Commands Manual FADES(1)


fades - A system that automatically handles the virtualenvs in the cases normally found when writing scripts and simple programs, and even helps to administer big projects.


fades [-h][--help] [-V][--version] [-v][--verbose] [-q][--quiet] [-i][--ipython] [-d][--dependency] [-r][--requirement] [-x][--exec] [-p version][--python=version] [--rm=UUID] [--system-site-packages] [--virtualenv-options=options] [--pip-options=options] [--python-options=options] [--check-updates] [--clean-unused-venvs=max_days_to_keep] [--get-venv-dir] [--no-precheck-availability] [-a][--autoimport] [--freeze] [-m][--module] [--avoid-pip-upgrade] [child_program [child_options]]

fades can be used to execute directly your script, or put it with a #! at your script's beginning.


fades will automagically create a new virtualenv (or reuse a previous created one), installing the necessary dependencies, and execute your script inside that virtualenv, with the only requirement of executing the script with fades and also marking the required dependencies.

The first non-option parameter (if any) would be then the child program to execute, and any other parameters after that are passed as is to that child script.

fades can also be executed without passing a child script to execute: in this mode it will open a Python interactive interpreter inside the created/reused virtualenv (taking dependencies from --dependency or --requirement options). If --autoimport is given, it will automatically import all the installed dependencies.

If the child_program parameter is really an URL, the script will be automatically downloaded from there (supporting also the most common pastebins URLs:,, gist, etc.).


-h, --help
Show help about all the parameters and options, and quit.

-V, --version
Show the program version and info about the system, and quit.

-v, --verbose
Send all internal debugging lines to stderr, which may be very useful if any problem arises.

-q, --quiet
Don't show anything (unless it has a real problem), so the original script stderr is not polluted at all.

-i, --ipython
Runs IPython shell instead of python ones.

-d, --dependency
Specify dependencies through command line. This option can be specified multiple times (once per dependency), and each time the format is repository::dependency. The dependency may have versions specifications, and the repository is optional (it will infer it). Examples:

requests pypi::requests > 2.3 requests<=3 git+ vcs::git+

See more examples below for real command line usage explanations.

-r, --requirement
Read the dependencies from a file. Format in each line is the same than dependencies specified with --dependency. This option can be specified multiple times.

-p version, --python=version
Select which Python version to be used; the argument can be just the number (2.7), the whole name (python2.7) or the whole path (/usr/bin/python2.7). Of course, the corresponding version of Python needs to be installed in your system.

The dependencies can be indicated in multiple places (in the Python source file, with a comment besides the import, in a requirementsfile, and/or through command line. In case of multiple definitions of the same dependency, command line overrides everything else, and requirements file overrides what is specified in the source code.

-x, --exec
Execute the child_program in the context of the virtualenv. The child_program, which in this case becomes a mandatory parameter, can be just the executable name (relative to the venv's bin directory) or an absolute path.

--rm UUID
Remove a virtualenv by UUID. See --get-venv-dir option to easily find out the UUID.

Give the virtual environment access to thesystem site-packages dir

Extra options to be supplied to virtualenv. (this option can be used multiple times)

Extra options to be supplied to pip. (this option can be used multiple times)

Extra options to be supplied to python. (this option can be used multiple times)

Will check for updates in PyPI to verify if there are new versions for the requested dependencies. If a new version is available for a dependency, it will use it (if the dependency was requested without version) or just inform which new version is available (if the dependency was requested with a specific version).

Will remove all virtualenvs that haven't been used for more than MAX_DAYS_TO_KEEP days.

Show the virtualenv base directory (which includes the virtualenv UUID) and quit.

Don't check if the packages exists in PyPI before actually try to install them.

-a, --autoimport
Automatically import the dependencies when in interactive interpreter mode (ignored otherwise).

--freeze FILEPATH
Will operate exactly as without the command, but also it will dump the revisions of installed dependencies to the given filepath.

-m, --module
Run library module as a script (same behaviour than Python's -m parameter).

Disable the automatic pip upgrade that happens after the virtualenv is created and before the dependencies begin to be installed.


fades --bar

Executes under fades, passing the --bar parameter to the child program, in a virtualenv with the dependencies indicated in the source code.

fades -v

Executes under fades, showing all the fades messages (verbose mode).

fades -d dependency1 -d dependency2>3.2 --bar

Executes under fades (passing the --bar parameter to it), in a virtualenv with the dependencies indicated in the source code and also dependency1 and dependency2 (any version > 3.2).

fades -d dependency1

Executes the Python interactive interpreter in a virtualenv with dependency1 installed.

fades -r requirements.txt

Executes the Python interactive interpreter in a virtualenv after installing there all dependencies taken from the requirements.txt file.

fades -r requirements.txt -r requirements_devel.txt

Executes the Python interactive interpreter in a virtualenv after installing there all dependencies taken from files requirements.txt and requirements_devel.txt.


You can also configure fades using .ini config files. fades will search config files in /etc/fades/fades.ini, the path indicated by xdg for your system (for example ~/config/fades/fades.ini) and .fades.ini. So you can have different settings at system, user and project level.

The config files are in .ini format. (configparser) and fades will search for a [fades] section. You have to use the same configurations that in the CLI. The only difference is with the config options with a dash, it has to be replaced with a underscore.

Check for full examples.


Development is centralized in

Check that site for a better explanation of fades usage.


Facundo Batista, Nicolás Demarchi (see development page for contact info).


This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License version 3, as published by the Free Software Foundation.