* Replace the Python 2 pending removal notice/schedule with a brief
message about the removal
* Replace mentions of "Python & Python 3" with just "Python" (references
to the version number are kept only in cases where it is necessary)
* Update Makefile example code to use Python 3 conventions/names
Signed-off-by: Jeffery To <jeffery.to@gmail.com>
3. [Wrapping things up so that they build](#wrapping-things-up-so-that-they-build)
4. [Customizing things](#customizing-things)
@ -22,49 +19,21 @@
This section describes specifics for the Python packages that are present in this repo, and how things are structured.
In terms of license, contributing guide, etc, all of that information is described in the top [README.md](README.md) file, and it applies here as well. This document attempts to cover only technical aspects of Python/Python3 packages, and maybe some explanations about how things are (and why they are as they are).
## Python 2 end-of-life
Python 2 will not be maintained past [1 January 2020](https://pythonclock.org/). As such, we will be transitioning Python 2 programs and libraries to Python 3, and Python 2 packages will be removed in early 2020.
(Discussion for how to handle this transition can be found in [#8520](https://github.com/openwrt/packages/issues/8520).)
### Transition policy / schedule
A mass removal event ("The Snap") will occur on 31 March 2020, or 2 weeks before the freeze for a 20.x release, whichever is sooner. The exact date will be confirmed when the 20.x release schedule is known, or by 15 March 2020.
All Python 2 packages (the Python 2 interpreter, programs that depend on Python 2, and Python 2-only libraries) will be removed during this event.
Leading up to "The Snap":
* In general, new Python 2 packages are no longer accepted
* Exceptions can be made on a case-by-case basis, given extraordinary circumstances or reasons, until 31 May 2019
* From 31 May 2019 onward, absolutely no new Python 2 packages will be accepted
* The Python 2 interpreter will remain in the feed until "The Snap"
* The interpreter will continue to be updated, including the last release in January 2020 (if there is one)
* Programs that depend on Python 2 will be transitioned to Python 3 (see [#8893](https://github.com/openwrt/packages/issues/8893))
* If a program cannot be transitioned, a suitable replacement will be found
* If a replacement cannot be found, the program will be removed during "The Snap"
* Python 2 libraries will remain in the feed until "The Snap"
* For any Python 2-only libraries, a Python 3 version will be added (or a suitable replacement found), if its Python 3 version is a dependency of another package in the feed
* Python 2 libraries will receive normal updates until 31 October 2019
* From 31 October 2019 onward:
* Python 2-only libraries will receive security updates only
* Python 2 libraries that share the same Makefile as their Python 3 version will continue to receive normal updates
In terms of license, contributing guide, etc, all of that information is described in the top [README.md](README.md) file, and it applies here as well. This document attempts to cover only technical aspects of Python packages, and maybe some explanations about how things are (and why they are as they are).
## Introduction
This sub-tree came to exist after a number of contributions (Python packages) were made to this repo, and the [lang](lang) subtree grew to a point where a decision was made to move all Python packages under [lang/python](lang/python).
It contains the 2 Python interpreters (Python & Python3) and Python packages. Most of the Python packages are downloaded from [pypi.org](https://pypi.org/). Python packages from [pypi.org](https://pypi.org/) are typically preferred when adding new packages.
It contains the Python 3 interpreter and Python packages. Most of the Python packages are downloaded from [pypi.org](https://pypi.org/). Python packages from [pypi.org](https://pypi.org/) are typically preferred when adding new packages.
If more packages (than the ones packaged here) are needed, they can be downloaded via [pip](https://pip.pypa.io). Note that the versions of `pip`&`setuptools` [available in this repo] are the ones that are packaged inside the Python package (yes, Python comes packaged with `pip`&`setuptools`).
If more packages (than the ones packaged here) are needed, they can be downloaded via [pip or pip3](https://pip.pypa.io). Note that the versions of `pip`&`setuptools` [available in this repo] are the ones that are packaged inside the Python & Python3 packages (yes, Python & Python3 come packaged with `pip`&`setuptools`).
## Python 2 end-of-life
Python 2 [will not be maintained past 2020](https://www.python.org/dev/peps/pep-0373/). All Python 2 packages have been removed from the packages feed (this repo) and archived in the [abandoned packages feed](https://github.com/openwrt/packages-abandoned).
## Using Python[3] in external/other package feeds
## Using Python in external/other package feeds
In the feeds.conf (or feeds.conf.default file, whatever is preferred), the packages repo should be present.
Assuming that there are Python packages in the `<some-other-package>`, they should include `python[3]-package.mk` like this:
Assuming that there are Python packages in the `<some-other-package>`, they should include `python3-package.mk` like this:
```
include $(TOPDIR)/feeds/packages/lang/python/python-package.mk
include $(TOPDIR)/feeds/packages/lang/python/python3-package.mk
```
Same rules apply for `python[3]-package.mk` as the Python packages in this repo.
And if only 1 of `python-package.mk` or `python3-package.mk` is needed, then only the needed mk file should be included (though it's not an issue if both are included).
Same rules apply for `python3-package.mk` as the Python packages in this repo.
**One important consideration:**: if the local name is not `packages`, it's something else, like `openwrt-packages`. And in `feeds.conf[.default]` it's:
include $(TOPDIR)/feeds/openwrt-packages/lang/python/python-package.mk
include $(TOPDIR)/feeds/openwrt-packages/lang/python/python3-package.mk
```
@ -104,86 +70,73 @@ Each maintainer[s] of external packages feeds is responsible for the local name,
In case there is a need/requirement such that the local package feed is named something else than `packages`, one approach to make the package flexible to change is:
# verify that there is only one single file returned
ifneq (1,$(words $(PYTHON_PACKAGE_MK)))
ifeq (0,$(words $(PYTHON_PACKAGE_MK)))
$(error did not find python-package.mk in any feed)
ifneq (1,$(words $(PYTHON3_PACKAGE_MK)))
ifeq (0,$(words $(PYTHON3_PACKAGE_MK)))
$(error did not find python3-package.mk in any feed)
else
$(error found multiple python-package.mk files in the feeds)
$(error found multiple python3-package.mk files in the feeds)
endif
else
$(info found python-package.mk at $(PYTHON_PACKAGE_MK))
$(info found python3-package.mk at $(PYTHON3_PACKAGE_MK))
endif
include $(PYTHON_PACKAGE_MK)
include $(PYTHON3_PACKAGE_MK)
```
Same can be done for `python3-package.mk`.
This should solve the corner-case where the `python[3]-package.mk` can be in some other feed, or if the packages feed will be named something else locally.
This should solve the corner-case where the `python3-package.mk` can be in some other feed, or if the packages feed will be named something else locally.
## Build considerations
In order to build the Python[3] interpreters, a host Python/Python3 interpreter needs to be built, in order to process some of the build for the target Python/Python3 build. The host Python[3] interpreters are also needed so that Python bytecodes are generated, so the host interpreters need to be the exact versions as on the target. And finally, the host Python[3] interpreters also provide pip & pip3, so that they may be used to install some Python[3] packages that are required to build other Python[3] packages.
That's why you'll also see a Python/Python3 build & staging directories.
In order to build the Python interpreter, a host Python interpreter needs to be built, in order to process some of the build for the target Python build. The host Python interpreter is also needed so that Python bytecodes are generated, so the host interpreter needs to be the exact version as on the target. And finally, the host Python interpreter also provides pip, so that it may be used to install some Python packages that are required to build other Python packages.
That's why you'll also see a Python build & staging directories.
As you're probably thinking, this sounds [and is] somewhat too much complication [just for packaging], but the status of things is-as-it-is, and it's probably much worse than what's currently visible on the surface [with respect to packaging Python[3]& packages].
As you're probably thinking, this sounds [and is] somewhat too much complication [just for packaging], but the status of things is-as-it-is, and it's probably much worse than what's currently visible on the surface [with respect to packaging Python & packages].
As mentioned earlier, Python[3] packages are shipped with bytecodes, and the reason for this is simply performance & size.
As mentioned earlier, Python packages are shipped with bytecodes, and the reason for this is simply performance & size.
The thought/discussion matrix derives a bit like this:
* shipping both Python source-code & bytecodes takes too much space on some devices ; Python source code & byte-code take about similar disk-size
* shipping only Python source code has a big performance penalty [on some lower end systems] ; something like 500 msecs (Python source-only) -> 70 msecs (Python byte-codes) time reduction for a simple "Hello World" script
* shipping only Python byte-codes seems like a good trade-off, and this means that `python-src`&`python3-src` can be provided for people that want the source code
* shipping only Python byte-codes seems like a good trade-off, and this means that `python3-src` can be provided for people that want the source code
By default, automatic Python[3] byte-code generation is disabled when running a Python script, in order to prevent a disk from accidentally filling up. Since some disks reside in RAM, this also means not filling up the RAM. If someone wants to convert Python source to byte-code then he/she is free to compile it [directly on the device] manually via the Python interpreter & library.
By default, automatic Python byte-code generation is disabled when running a Python script, in order to prevent a disk from accidentally filling up. Since some disks reside in RAM, this also means not filling up the RAM. If someone wants to convert Python source to byte-code then he/she is free to compile it [directly on the device] manually via the Python interpreter & library.
## General folder structure
The basis of all these packages are:
* [lang/python/python](lang/python/python) - The Python 2.7.y interpreter (supposedly, there won't ever by a 2.8.y)
The basis of all these packages is:
* [lang/python/python3](lang/python/python3) - The Python 3.x.y interpreter
These 2 are normal OpenWrt packages, which will build the Python interpreters. They also provide `python[3]-pip`&`python[3]-setuptools`. Each Python or Python3 package is actually split into multiple sub-packages [e.g. python-email, python-sqlite3, etc]. This can be viewed inside [lang/python/python/files](lang/python/python/files) & [lang/python/python3/files](lang/python/python3/files).
The reason for this splitting, is purely to offer a way for some people to package Python/Python3 in as-minimal-as-possible-and-still-runable way, and also to be somewhat maintainable when packaging. A standard Python[3] installation can take ~20-30 MBs of disk, which can be somewhat big for some people, so there are the `python[3]-base` packages which bring that down to ~5 MBs. This seems to be good enough (and interesting) for a number of people.
This is a normal OpenWrt package, which will build the Python interpreter. This also provides `python3-pip`&`python3-setuptools`. Each Python package is actually split into multiple sub-packages [e.g. python3-email, python3-sqlite3, etc]. This can be viewed inside [lang/python/python3/files](lang/python/python3/files).
The Python[3] interpreters are structured like this:
* `python-base` (and `python3-base`), which is just the minimal package to startup Python[3] and run basic commands
* `python` (and `python3`) are meta-packages, which install almost everything (python[3]-base [plus] Python[3] library [minus] some unit-tests & some windows-y things)
* `python-light` (and `python3-light`) are `python` (and `python3`) [minus] packages that are in [lang/python/python/files](lang/python/python/files) or [lang/python/python3/files](lang/python/python3/files) ; the size of these 2 packages may be sensible (and interesting) to another group of people
The reason for this splitting, is purely to offer a way for some people to package Python in as-minimal-as-possible-and-still-runable way, and also to be somewhat maintainable when packaging. A standard Python installation can take ~20-30 MBs of disk, which can be somewhat big for some people, so there is the `python3-base` package which brings that down to ~5 MBs. This seems to be good enough (and interesting) for a number of people.
All other Python & Python3 packages (aside from the 2 intepreters) typically use these files:
* **python[3]-host.mk** - this file contains paths and build rules for running the Python[3] interpreters on the host-side; they also provide paths to host interprete, host Python lib-dir & so on
* **python[3]-package.mk**
* includes **python[3]-host.mk**
* contains all the default build rules for Python[3] packages; these will be detailed below in the [Building a Python[3] package](#Building a Python[3] package) section
The Python interpreter is structured like this:
* `python3-base`, which is just the minimal package to startup Python and run basic commands
* `python3` is a meta-package, which installs almost everything (python3-base [plus] Python library [minus] some unit-tests & some windows-y things)
* `python3-light` is `python3` [minus] packages that are in [lang/python/python3/files](lang/python/python3/files) ; the size of this package may be sensible (and interesting) to another group of people
**Note** that Python/Python3 packages don't need to use these files (i.e. `python[3]-package.mk`&`python[3]-host.mk`), but they do provide some ease-of-use & reduction of duplicate code, especially when packaging for both Python & Python3. And they do contain some learned-lessons about packaging Python/Python3 packages, so it's a good idea to use them.
All other Python packages (aside from the intepreter) typically use these files:
* **python3-host.mk** - this file contains paths and build rules for running the Python interpreter on the host-side; they also provide paths to host interprete, host Python lib-dir & so on
* **python3-package.mk**
* includes **python3-host.mk**
* contains all the default build rules for Python packages; these will be detailed below in the [Building a Python package](#Building a Python package) section
## Building a Python[3] package
**Note** that Python packages don't need to use these files (i.e. `python3-package.mk`&`python3-host.mk`), but they do provide some ease-of-use & reduction of duplicate code. And they do contain some learned-lessons about packaging Python packages, so it's a good idea to use them.
A Python package can be packaged for either Python or Python3 or both.
## Building a Python package
This section will describe both, and then it can be inferred which is for which.
Packaging for Python uses the `VARIANT` mechanism for packaging inside OpenWrt. (#### FIXME: find a link for this later if it exists)
Packaging for both Python & Python3 uses the `VARIANT` mechanism for packaging inside OpenWrt. (#### FIXME: find a link for this later if it exists)
### Include python3-package.mk
### Include python[3]-package.mk
If packaging for Python, add this after `include $(INCLUDE_DIR)/package.mk`
```
include ../python-package.mk
```
If packaging for Python3, add this after `include $(INCLUDE_DIR)/package.mk`
Add this after `include $(INCLUDE_DIR)/package.mk`
```
include ../python3-package.mk
```
Order doesn't matter between `python-package.mk`&`python3-package.mk`.
These will make sure that build rules for Python or Python3 can be specified and picked up for build.
This will make sure that build rules for Python can be specified and picked up for build.
### Include pypi.mk (optional)
@ -225,98 +178,58 @@ The `PYPI_SOURCE_*` variables allow this default `PKG_SOURCE` value to be custom
### Add Package/<PKG_NAME> OpenWrt definitions
This part is similar to default OpenWrt packages.
It's usually recommended to have a `Package/<PKG_NAME>/Default` section that's common for both Python & Python3.
Some considerations here (based on the example above):
* be sure to make sure that `DEPENDS` are correct for both variants; as seen in the example above, `python-codecs` is needed only for `python-lxml` (see **[note-encodings](#note-encodings)**)
* consider adding conditional DEPENDS for each variant ; so for each Python[3] package add `+PACKAGE_python-lxml:<dep>` as seen in the above example ; the reason for this is build-time reduction ; if you want to build Python3 only packages, this won't build Python & Python packages + dependencies ; this is a known functionality of OpenWrt build deps
* this should not happen anymore, but if adding `+PACKAGE_python-lxml` conditional deps creates circular dependencies, then open an issue so this can be resolved again.
* `VARIANT=python` or `VARIANT=python3` must be added
* typically each variant package is named `Package/python-<something>`&`Package/python3-<something>` ; this convention makes things easier to follow, though it could work without naming things this way
* `TITLE` can be something a bit more verbose/neat ; typically the name is short as seen above
<aname="note-encodings">**note-encodings**</a>: That's because some character encodings are needed, which are present in `python3-base` but not in `python-light` (but are present in `python-codecs`) ; this is because Python3 is designed to be more Unicode friendly than Python2 (it's one of the fundamental differences between the 2), and Python3 won't start without those encodings being present.
Following these, 2 more definitions are required:
```
define Package/python-lxml/description
The lxml XML toolkit is a Pythonic binding
for the C libraries libxml2 and libxslt.
endef
define Package/python3-lxml/description
$(call Package/python-lxml/description)
.
(Variant for Python3)
The lxml XML toolkit is a Pythonic binding
for the C libraries libxml2 and libxslt.
endef
```
Typically, the description is the same for both, so just mentioning that one is a variant of the other is sufficient.
Some considerations here (based on the example above):
* `VARIANT=python3` must be added
* typically the package is named `Package/python3-<something>` ; this convention makes things easier to follow, though it could work without naming things this way
* `TITLE` can be something a bit more verbose/neat ; typically the name is short as seen above
### Wrapping things up so that they build
If all the above prerequisites have been met, all that's left is:
```
$(eval $(call PyPackage,python-lxml))
$(eval $(call BuildPackage,python-lxml))
$(eval $(call Py3Package,python3-lxml))
$(eval $(call BuildPackage,python3-lxml))
```
The `$(eval $(call PyPackage,python-lxml))` part will instantiate all the default Python build rules so that the final Python package is packaged into an OpenWrt.
And `$(eval $(call BuildPackage,python-lxml))` will bind all the rules generated with `$(eval $(call PyPackage,python-lxml))` into the OpenWrt build system.
The `$(eval $(call Py3Package,python3-lxml))` part will instantiate all the default Python build rules so that the final Python package is packaged into an OpenWrt.
And `$(eval $(call BuildPackage,python3-lxml))` will bind all the rules generated with `$(eval $(call Py3Package,python3-lxml))` into the OpenWrt build system.
These packages will contain byte-codes and binaries (shared libs & other stuff).
If a user wishes to ship source code, adding 2 more lines creates 2 more packages that ship Python source code:
If a user wishes to ship source code, adding one more line creates one more package that ship Python source code:
```
$(eval $(call PyPackage,python-lxml))
$(eval $(call BuildPackage,python-lxml))
$(eval $(call BuildPackage,python-lxml-src))
$(eval $(call Py3Package,python3-lxml))
$(eval $(call BuildPackage,python3-lxml))
$(eval $(call BuildPackage,python3-lxml-src))
```
The name `*-src` must be the Python package name; so for `python-lxml-src` a equivalent `python-lxml` name must exist.
The name `*-src` must be the Python package name; so for `python3-lxml-src` a equivalent `python3-lxml` name must exist.
### Customizing things
Some packages need custom build rules (because they do).
The default package build and install processes are defined in `python[3]-package.mk`.
The default package build and install processes are defined in `python3-package.mk`.
#### Building
@ -324,35 +237,35 @@ The default build process calls `setup.py install` inside the directory where th
There are several Makefile variables that can be used to customize this process (all optional):
* `PYTHON_PKG_SETUP_DIR` / `PYTHON3_PKG_SETUP_DIR`: Path where `setup.py` can be found, relative to the package directory (`PKG_BUILD_DIR`).
* `PYTHON3_PKG_SETUP_DIR`: Path where `setup.py` can be found, relative to the package directory (`PKG_BUILD_DIR`).
Default: empty value (`setup.py` is in the package directory)
* `PYTHON_PKG_SETUP_VARS` / `PYTHON3_PKG_SETUP_VARS`: Additional environment variables to set for the call to `setup.py`. Should be in the form of `VARIABLE1=value VARIABLE2=value ...`.
* `PYTHON3_PKG_SETUP_VARS`: Additional environment variables to set for the call to `setup.py`. Should be in the form of `VARIABLE1=value VARIABLE2=value ...`.
Default: empty value
* `PYTHON_PKG_SETUP_GLOBAL_ARGS` / `PYTHON3_PKG_SETUP_GLOBAL_ARGS`: Additional command line arguments to pass to `setup.py`, before / in front of the `install` command.
* `PYTHON3_PKG_SETUP_GLOBAL_ARGS`: Additional command line arguments to pass to `setup.py`, before / in front of the `install` command.
Default: empty value
* `PYTHON_PKG_SETUP_ARGS` / `PYTHON3_PKG_SETUP_ARGS`: Additional command line arguments to pass to `setup.py`, after the `install` command.
* `PYTHON3_PKG_SETUP_ARGS`: Additional command line arguments to pass to `setup.py`, after the `install` command.
Default: `--single-version-externally-managed`
Conceptually, these variables are used in this way (using a Python 2 package as an example):
Conceptually, these variables are used in this way:
The default build process can be completely overridden by defining custom `PyBuild/Compile`&`Py3Build/Compile` rules in the package Makefile.
The default build process can be completely overridden by defining a custom `Py3Build/Compile` rule in the package Makefile.
#### Installing
The default install process copies some/all of the files from `PKG_INSTALL_DIR`, placed there by the build process, to a location passed to the install rule as the first argument (`$(1)`). The OpenWrt build system will then take those files and create the actual .ipk package archives.
This default process uses 2 build rules:
* `PyPackage/<package>/filespec`&`Py3Package/<package>/filespec` which are Python library files relative to `/usr/lib/pythonX.Y` ; by default this is `/usr/lib/python$(PYTHON[3]_VERSION)/site-packages` (`PYTHON[3]_PKG_DIR`) ; most Python[3] packages generate files that get installed in this sub-folder
* `PyPackage/<package>/install`&`Py3Package/<package>/install` is similar to `Package/<package>/install` ; these allow binary (or other files) to be installed on the target
* `Py3Package/<package>/filespec` which are Python library files relative to `/usr/lib/pythonX.Y` ; by default this is `/usr/lib/python$(PYTHON3_VERSION)/site-packages` (`PYTHON3_PKG_DIR`) ; most Python packages generate files that get installed in this sub-folder
* `Py3Package/<package>/install` is similar to `Package/<package>/install` ; this allows binary (or other files) to be installed on the target
Both the 2 above rules generate a `Package/<package>/install` build rule, which gets picked up by the build system. Both can be used together (they are not mutually exclusive), and provide a good enough flexibility for specifying Python[3] packages.
Both the 2 above rules generate a `Package/<package>/install` build rule, which gets picked up by the build system. Both can be used together (they are not mutually exclusive), and provide a good enough flexibility for specifying Python packages.
The `PyPackage/<package>/filespec`&`Py3Package/<package>/filespec` rules contain one or more lines of the following format (whitespace added for clarity):
The `Py3Package/<package>/filespec` rule contains one or more lines of the following format (whitespace added for clarity):
@ -366,21 +279,21 @@ The initial character controls the action that will be taken:
* File permissions is not used / ignored in this case.
* `=`: Assign the given file permissions to the given path. File permissions is required in this case.
As mentioned, the default `PyPackage/<package>/filespec`&`Py3Package/<package>/filespec` install `PYTHON[3]_PKG_DIR`:
As mentioned, the default `Py3Package/<package>/filespec` installs`PYTHON3_PKG_DIR`:
```
define PyPackage/python-example/filespec
+|$(PYTHON_PKG_DIR)
define Py3Package/python3-example/filespec
+|$(PYTHON3_PKG_DIR)
endef
```
If the package installs a `example_package` directory inside `PYTHON_PKG_DIR`, and there is an `examples` directory and `test_*.py` files that can be omitted to save space, this can be specified as:
If the package installs a `example_package` directory inside `PYTHON3_PKG_DIR`, and there is an `examples` directory and `test_*.py` files that can be omitted to save space, this can be specified as:
```
define PyPackage/python-example/filespec
+|$(PYTHON_PKG_DIR)
-|$(PYTHON_PKG_DIR)/example_package/examples
-|$(PYTHON_PKG_DIR)/example_package/test_*.py
define Py3Package/python3-example/filespec
+|$(PYTHON3_PKG_DIR)
-|$(PYTHON3_PKG_DIR)/example_package/examples
-|$(PYTHON3_PKG_DIR)/example_package/test_*.py
endef
```
@ -390,9 +303,8 @@ These can be installed via pip and ideally they should only be installed like th
Which is why [for example] if you need python cffi on the host build, it's easier to just add it via:
[cffi is one of those packages that needs a host-side package installed for both Python & Python3].
[cffi is one of those packages that needs a host-side package installed].
This works reasonably well in the current OpenWrt build system, as binaries get built for this package and get installed in the staging-dir `$(STAGING_DIR)/usr/lib/pythonX.Y/site-packages`.
Jeffery To
5 years ago