[PULL 06/15] python: Add no-install usage instructions

From: John Snow <jsnow@redhat.com>
To: qemu-devel@nongnu.org
Cc: "Peter Maydell" <peter.maydell@linaro.org>,
	"Thomas Huth" <thuth@redhat.com>,
	"Eduardo Habkost" <ehabkost@redhat.com>,
	"Alex Bennée" <alex.bennee@linaro.org>,
	"Markus Armbruster" <armbru@redhat.com>,
	"Wainer dos Santos Moschetta" <wainersm@redhat.com>,
	"Philippe Mathieu-Daudé" <f4bug@amsat.org>,
	"Willian Rampazzo" <willianr@redhat.com>,
	"Cleber Rosa" <crosa@redhat.com>, "John Snow" <jsnow@redhat.com>
Subject: [PULL 06/15] python: Add no-install usage instructions
Date: Wed, 30 Jun 2021 22:09:12 -0400	[thread overview]
Message-ID: <20210701020921.1679468-7-jsnow@redhat.com> (raw)
In-Reply-To: <20210701020921.1679468-1-jsnow@redhat.com>

It's not encouraged, but it's legitimate to want to know how to do.

Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Willian Rampazzo <willianr@redhat.com>
Reviewed-by: Wainer dos Santos Moschetta <wainersm@redhat.com>
Message-id: 20210629214323.1329806-7-jsnow@redhat.com
Signed-off-by: John Snow <jsnow@redhat.com>
---
 python/README.rst | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/python/README.rst b/python/README.rst
index 107786ffdc..d4502fdb60 100644
--- a/python/README.rst
+++ b/python/README.rst
@@ -37,6 +37,34 @@ See `Installing packages using pip and virtual environments
 for more information.
 
 
+Using these packages without installing them
+--------------------------------------------
+
+These packages may be used without installing them first, by using one
+of two tricks:
+
+1. Set your PYTHONPATH environment variable to include this source
+   directory, e.g. ``~/src/qemu/python``. See
+   https://docs.python.org/3/using/cmdline.html#envvar-PYTHONPATH
+
+2. Inside a Python script, use ``sys.path`` to forcibly include a search
+   path prior to importing the ``qemu`` namespace. See
+   https://docs.python.org/3/library/sys.html#sys.path
+
+A strong downside to both approaches is that they generally interfere
+with static analysis tools being able to locate and analyze the code
+being imported.
+
+Package installation also normally provides executable console scripts,
+so that tools like ``qmp-shell`` are always available via $PATH. To
+invoke them without installation, you can invoke e.g.:
+
+``> PYTHONPATH=~/src/qemu/python python3 -m qemu.qmp.qmp_shell``
+
+The mappings between console script name and python module path can be
+found in ``setup.cfg``.
+
+
 Files in this directory
 -----------------------
 
-- 
2.31.1


