[Merge after v2.11.0 Release] Retire support for Python 3.9 (#3683)

.github/workflows/install-from-conda.yml

@@ -20,7 +20,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: ["3.9", "3.10", "3.11"]
+        python-version: ["3.10", "3.11"]
     name: Linux Python ${{ matrix.python-version }}
     steps:
       - uses: conda-incubator/setup-miniconda@v3
@@ -56,7 +56,7 @@ jobs:
 #    runs-on: "macos-latest"
 #    strategy:
 #      matrix:
-#        python-version: ["3.9", "3.10", "3.11"]
+#        python-version: ["3.10", "3.11"]
 #      fail-fast: false
 #    name: OSX Python ${{ matrix.python-version }}
 #    steps:

.github/workflows/install-from-condalock-file.yml

@@ -30,7 +30,7 @@ jobs:
     runs-on: "ubuntu-latest"
     strategy:
       matrix:
-        python-version: ["3.9", "3.10", "3.11"]
+        python-version: ["3.10", "3.11"]
       fail-fast: false
     name: Linux Python ${{ matrix.python-version }}
     steps:

.github/workflows/install-from-source.yml

@@ -19,7 +19,7 @@ jobs:
     runs-on: "ubuntu-latest"
     strategy:
       matrix:
-        python-version: ["3.9", "3.10", "3.11"]
+        python-version: ["3.10", "3.11"]
       fail-fast: false
     name: Linux Python ${{ matrix.python-version }}
     steps:
@@ -59,7 +59,7 @@ jobs:
 #    runs-on: "macos-latest"
 #    strategy:
 #      matrix:
-#        python-version: ["3.9", "3.10", "3.11"]
+#        python-version: ["3.10", "3.11"]
 #      fail-fast: false
 #    name: OSX Python ${{ matrix.python-version }}
 #    steps:

.github/workflows/run-tests-monitor.yml

@@ -23,7 +23,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: ["3.9", "3.10", "3.11"]
+        python-version: ["3.10", "3.11"]
     name: Linux Python ${{ matrix.python-version }}
     steps:
       - uses: actions/checkout@v4
@@ -67,7 +67,7 @@ jobs:
     runs-on: "macos-latest"
     strategy:
       matrix:
-        python-version: ["3.9", "3.10", "3.11"]
+        python-version: ["3.10", "3.11"]
         architecture: ["x64"]  # need to force Intel, arm64 builds have issues
       fail-fast: false
     name: OSX Python ${{ matrix.python-version }}

.github/workflows/test-development.yml

@@ -26,7 +26,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: ["3.9", "3.10", "3.11"]
+        python-version: ["3.10", "3.11"]
     name: Linux Python ${{ matrix.python-version }}
     steps:
       - uses: actions/checkout@v4

.github/workflows/test.yml

@@ -20,7 +20,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: ["3.9", "3.10", "3.11"]
+        python-version: ["3.10", "3.11"]
     name: Linux Python ${{ matrix.python-version }}
     steps:
       - uses: actions/checkout@v4
@@ -72,7 +72,7 @@ jobs:
     runs-on: "macos-latest"
     strategy:
       matrix:
-        python-version: ["3.9", "3.10", "3.11"]
+        python-version: ["3.10", "3.11"]
         architecture: ["x64"]  # need to force Intel, arm64 builds have issues
       fail-fast: false
     name: OSX Python ${{ matrix.python-version }}

doc/sphinx/source/quickstart/installation.rst

@@ -8,7 +8,7 @@ Installation
    ESMValTool now uses `mamba` instead of `conda` for the recommended installation.
    For more information about the change, have a look at :ref:`Move to Mamba<move-to-mamba>`.
 
-ESMValTool supports Python 3.9 and later and requires Linux or MacOS.
+ESMValTool supports Python 3.10 and later and requires Linux or MacOS.
 Successful usage on Windows has been reported by following the Linux
 installation instructions with
 `WSL <https://learn.microsoft.com/en-us/windows/wsl/install>`__.
@@ -489,7 +489,7 @@ To check that the installation was successful, run
 this should show the directory of the source code that you just downloaded.
 
 If the command above shows a directory inside your conda environment instead,
-e.g. ``~/mambaforge/envs/esmvaltool/lib/python3.9/site-packages/esmvalcore``,
+e.g. ``~/mambaforge/envs/esmvaltool/lib/python3.11/site-packages/esmvalcore``,
 you may need to manually remove that directory and run
 ``pip install --editable '.[develop]'`` again.
 
@@ -684,40 +684,6 @@ repository, a direct download link can be found `here <https://raw.githubusercon
 Common installation problems and their solutions
 ================================================
 
-Mamba fails to solve the environment
-------------------------------------
-If you see the text ``Solving environment:`` with the characters ``-\|/`` rotating
-behind it for more than 10 minutes, mamba may be having problems finding a
-working combination of versions of the packages that the ESMValTool depends on.
-Because the ESMValTool is a community tool, there is no strict selection of
-which tools can be used and installing the ESMValTool requires installing almost
-any package that is available for processing climate data.
-To help mamba solve the environment, you can try the following.
-
-Always use the latest version of mamba, as problems have been reported by people
-using older versions, to update, run:
-
-.. code-block:: bash
-
-    mamba update --name base mamba
-
-Usually mamba is much better at solving new environments than updating older
-environments, so it is often a good idea to create a new environment if updating
-does not work.
-
-It can help mamba if you let it know what version of certain packages you want,
-for example by running
-
-.. code-block:: bash
-
-    mamba create -n esmvaltool esmvaltool 'python=3.11'
-
-you ask for Python 3.11 specifically and that makes it much easier for mamba to
-solve the environment, because now it can ignore any packages that were built
-for other Python versions. Note that, since the esmvaltool package is built
-with Python>=3.9, asking for an older Python version, e.g. `python=3.7`, in
-this way, it will result in installation failure.
-
 Problems with proxies
 ---------------------
 If you are installing ESMValTool from source from behind a proxy that does not
@@ -778,7 +744,7 @@ Problems when updating the conda environment
 --------------------------------------------
 Usually mamba is much better at solving new environments than updating older
 environments, so it is often a good idea to create a new environment if updating
-does not work. See also `Mamba fails to solve the environment`_.
+does not work.
 
 Do not run ``mamba update --update-all`` in the ``esmvaltool``
 environment since that will update some packages that are pinned to

environment.yml

@@ -51,7 +51,7 @@ dependencies:
   - psy-simple
   - pyproj >=2.1
   - pys2index  # only from conda-forge
-  - python >=3.9
+  - python >=3.10
   - python-cdo
   - python-dateutil
   - pyyaml

environment_osx.yml

@@ -51,7 +51,7 @@ dependencies:
   - psy-simple
   - pyproj >=2.1
   - pys2index  # only from conda-forge
-  - python >=3.9
+  - python >=3.10
   - python-cdo
   - python-dateutil
   - pyyaml

setup.py

@@ -221,7 +221,6 @@ def read_description(filename):
         'Natural Language :: English',
         'Operating System :: POSIX :: Linux',
         'Programming Language :: Python :: 3',
-        'Programming Language :: Python :: 3.9',
         'Programming Language :: Python :: 3.10',
         'Programming Language :: Python :: 3.11',
         'Topic :: Scientific/Engineering',