Resolve default imports for optional dependencies

CHANGELOG.md

@@ -2,7 +2,7 @@
 
 ## Bug fixes
 
-- Fixed a bug where the JaxSolver would fails when using GPU support with no input parameters ([#3423](https://github.com/pybamm-team/PyBaMM/pull/3423))
+- Fixed bug in calculation of theoretical energy that made it very slow ([#3506](https://github.com/pybamm-team/PyBaMM/pull/3506))
 
 # [v23.9rc0](https://github.com/pybamm-team/PyBaMM/tree/v23.9rc0) - 2023-10-31
 
@@ -23,6 +23,7 @@
 
 ## Bug fixes
 
+- Fixed a bug where the JaxSolver would fail when using GPU support with no input parameters ([#3423](https://github.com/pybamm-team/PyBaMM/pull/3423))
 - Fixed a bug where empty lists passed to QuickPlot resulted in an IndexError and did not return a meaningful error message ([#3359](https://github.com/pybamm-team/PyBaMM/pull/3359))
 - Fixed a bug where there was a missing thermal conductivity in the thermal pouch cell models ([#3330](https://github.com/pybamm-team/PyBaMM/pull/3330))
 - Fixed a bug that caused incorrect results of “{Domain} electrode thickness change [m]” due to the absence of dimension for the variable `electrode_thickness_change`([#3329](https://github.com/pybamm-team/PyBaMM/pull/3329)).
@@ -61,7 +62,7 @@
 - Added option to use an empirical hysteresis model for the diffusivity and exchange-current density ([#3194](https://github.com/pybamm-team/PyBaMM/pull/3194))
 - Double-layer capacity can now be provided as a function of temperature ([#3174](https://github.com/pybamm-team/PyBaMM/pull/3174))
 - `pybamm_install_jax` is deprecated. It is now replaced with `pip install pybamm[jax]` ([#3163](https://github.com/pybamm-team/PyBaMM/pull/3163))
-- PyBaMM now has optional dependencies that can be installed with the pattern `pip install pybamm[option]` e.g. `pybamm[plot]` ([#3044](https://github.com/pybamm-team/PyBaMM/pull/3044))
+- PyBaMM now has optional dependencies that can be installed with the pattern `pip install pybamm[option]` e.g. `pybamm[plot]` ([#3044](https://github.com/pybamm-team/PyBaMM/pull/3044), [#3475](https://github.com/pybamm-team/PyBaMM/pull/3475))
 
 # [v23.5](https://github.com/pybamm-team/PyBaMM/tree/v23.5) - 2023-06-18
 

CONTRIBUTING.md

@@ -100,21 +100,52 @@ On the other hand... We _do_ want to compare several tools, to generate document
 
 Only 'core pybamm' is installed by default. The others have to be specified explicitly when running the installation command.
 
-### Matplotlib
+### Managing Optional Dependencies and Their Imports
 
-We use Matplotlib in PyBaMM, but with two caveats:
+PyBaMM utilizes optional dependencies to allow users to choose which additional libraries they want to use. Managing these optional dependencies and their imports is essential to provide flexibility to PyBaMM users.
 
-First, Matplotlib should only be used in plotting methods, and these should _never_ be called by other PyBaMM methods. So users who don't like Matplotlib will not be forced to use it in any way. Use in notebooks is OK and encouraged.
+PyBaMM provides a utility function `have_optional_dependency`, to check for the availability of optional dependencies within methods. This function can be used to conditionally import optional dependencies only if they are available. Here's how to use it:
 
-Second, Matplotlib should never be imported at the module level, but always inside methods. For example:
+Optional dependencies should never be imported at the module level, but always inside methods. For example:
 
 ```
-def plot_great_things(self, x, y, z):
-    import matplotlib.pyplot as pl
+def use_pybtex(x,y,z):
+    pybtex = have_optional_dependency("pybtex")
     ...
 ```
 
-This allows people to (1) use PyBaMM without ever importing Matplotlib and (2) configure Matplotlib's back-end in their scripts, which _must_ be done before e.g. `pyplot` is first imported.
+While importing a specific module instead of an entire package/library:
+
+```python
+def use_parse_file(x, y, z):
+    parse_file = have_optional_dependency("pybtex.database", "parse_file")
+    ...
+```
+
+This allows people to (1) use PyBaMM without importing optional dependencies by default and (2) configure module-dependent functionalities in their scripts, which _must_ be done before e.g. `print_citations` method is first imported.
+
+**Writing Tests for Optional Dependencies**
+
+Whenever a new optional dependency is added for optional functionality, it is recommended to write a corresponding unit test in `test_util.py`. This ensures that an error is raised upon the absence of said dependency. Here's an example:
+
+```python
+from tests import TestCase
+import pybamm
+
+
+class TestUtil(TestCase):
+    def test_optional_dependency(self):
+        # Test that an error is raised when pybtex is not available
+        with self.assertRaisesRegex(
+            ModuleNotFoundError, "Optional dependency pybtex is not available"
+        ):
+            sys.modules["pybtex"] = None
+            pybamm.function_using_pybtex(x, y, z)
+
+        # Test that the function works when pybtex is available
+        sys.modules["pybtex"] = pybamm.util.have_optional_dependency("pybtex")
+        pybamm.function_using_pybtex(x, y, z)
+```
 
 ## Testing
 
@@ -266,7 +297,6 @@ This also means that, if you can't fix the bug yourself, it will be much easier
       ```
 
       This will start the debugger at the point where the `ValueError` was raised, and allow you to investigate further. Sometimes, it is more informative to put the try-except block further up the call stack than exactly where the error is raised.
-
    2. Warnings. If functions are raising warnings instead of errors, it can be hard to pinpoint where this is coming from. Here, you can use the `warnings` module to convert warnings to errors:
 
       ```python
@@ -276,19 +306,15 @@ This also means that, if you can't fix the bug yourself, it will be much easier
       ```
 
       Then you can use a try-except block, as in a., but with, for example, `RuntimeWarning` instead of `ValueError`.
-
    3. Stepping through the expression tree. Most calls in PyBaMM are operations on [expression trees](https://github.com/pybamm-team/PyBaMM/blob/develop/docs/source/examples/notebooks/expression_tree/expression-tree.ipynb). To view an expression tree in ipython, you can use the `render` command:
 
       ```python
       expression_tree.render()
       ```
 
       You can then step through the expression tree, using the `children` attribute, to pinpoint exactly where a bug is coming from. For example, if `expression_tree.jac(y)` is failing, you can check `expression_tree.children[0].jac(y)`, then `expression_tree.children[0].children[0].jac(y)`, etc.
-
 3. To isolate whether a bug is in a model, its Jacobian or its simplified version, you can set the `use_jacobian` and/or `use_simplify` attributes of the model to `False` (they are both `True` by default for most models).
-
 4. If a model isn't giving the answer you expect, you can try comparing it to other models. For example, you can investigate parameter limits in which two models should give the same answer by setting some parameters to be small or zero. The `StandardOutputComparison` class can be used to compare some standard outputs from battery models.
-
 5. To get more information about what is going on under the hood, and hence understand what is causing the bug, you can set the [logging](https://realpython.com/python-logging/) level to `DEBUG` by adding the following line to your test or script:
 
    ```python3

docs/source/user_guide/installation/index.rst

@@ -66,6 +66,7 @@ Package                                                          Minimum support
 `SciPy <https://docs.scipy.org/doc/scipy/>`__                    2.8.2
 `CasADi <https://web.casadi.org/docs/>`__                        3.6.0
 `Xarray <https://docs.xarray.dev/en/stable/>`__                  2023.04.0
+`Anytree <https://anytree.readthedocs.io/en/stable/>`__          2.4.3
 ================================================================ ==========================
 
 .. _install.optional_dependencies:

pybamm/__init__.py

@@ -47,13 +47,13 @@
     get_parameters_filepath,
     have_jax,
     install_jax,
+    have_optional_dependency,
     is_jax_compatible,
     get_git_commit_info,
 )
 from .logger import logger, set_logging_level, get_new_logger
 from .settings import settings
 from .citations import Citations, citations, print_citations
-
 #
 # Classes for the Expression Tree
 #

pybamm/citations.py

@@ -6,10 +6,8 @@
 import pybamm
 import os
 import warnings
-import pybtex
 from sys import _getframe
-from pybtex.database import parse_file, parse_string, Entry
-from pybtex.scanner import PybtexError
+from pybamm.util import have_optional_dependency
 
 
 class Citations:
@@ -76,6 +74,7 @@ def read_citations(self):
         """Reads the citations in `pybamm.CITATIONS.bib`. Other works can be cited
         by passing a BibTeX citation to :meth:`register`.
         """
+        parse_file = have_optional_dependency("pybtex.database", "parse_file")
         citations_file = os.path.join(pybamm.root_dir(), "pybamm", "CITATIONS.bib")
         bib_data = parse_file(citations_file, bib_format="bibtex")
         for key, entry in bib_data.entries.items():
@@ -86,6 +85,7 @@ def _add_citation(self, key, entry):
         previous entry is overwritten
         """
 
+        Entry = have_optional_dependency("pybtex.database", "Entry")
         # Check input types are correct
         if not isinstance(key, str) or not isinstance(entry, Entry):
             raise TypeError()
@@ -151,6 +151,8 @@ def _parse_citation(self, key):
         key: str
             A BibTeX formatted citation
         """
+        PybtexError = have_optional_dependency("pybtex.scanner", "PybtexError")
+        parse_string = have_optional_dependency("pybtex.database", "parse_string")
         try:
             # Parse string as a bibtex citation, and check that a citation was found
             bib_data = parse_string(key, bib_format="bibtex")
@@ -217,6 +219,7 @@ def print(self, filename=None, output_format="text", verbose=False):
         """
         # Parse citations that were not known keys at registration, but do not
         # fail if they cannot be parsed
+        pybtex = have_optional_dependency("pybtex")
         try:
             for key in self._unknown_citations:
                 self._parse_citation(key)

pybamm/expression_tree/array.py

@@ -2,10 +2,10 @@
 # NumpyArray class
 #
 import numpy as np
-import sympy
 from scipy.sparse import csr_matrix, issparse
 
 import pybamm
+from pybamm.util import have_optional_dependency
 
 
 class Array(pybamm.Symbol):
@@ -125,6 +125,7 @@ def is_constant(self):
 
     def to_equation(self):
         """Returns the value returned by the node when evaluated."""
+        sympy = have_optional_dependency("sympy")
         entries_list = self.entries.tolist()
         return sympy.Array(entries_list)
 

pybamm/expression_tree/binary_operators.py

@@ -4,11 +4,11 @@
 import numbers
 
 import numpy as np
-import sympy
 from scipy.sparse import csr_matrix, issparse
 import functools
 
 import pybamm
+from pybamm.util import have_optional_dependency
 
 
 def _preprocess_binary(left, right):
@@ -147,6 +147,7 @@ def _sympy_operator(self, left, right):
 
     def to_equation(self):
         """Convert the node and its subtree into a SymPy equation."""
+        sympy = have_optional_dependency("sympy")
         if self.print_name is not None:
             return sympy.Symbol(self.print_name)
         else:
@@ -323,6 +324,7 @@ def _binary_evaluate(self, left, right):
 
     def _sympy_operator(self, left, right):
         """Override :meth:`pybamm.BinaryOperator._sympy_operator`"""
+        sympy = have_optional_dependency("sympy")
         left = sympy.Matrix(left)
         right = sympy.Matrix(right)
         return left * right
@@ -626,6 +628,7 @@ def _binary_new_copy(self, left, right):
 
     def _sympy_operator(self, left, right):
         """Override :meth:`pybamm.BinaryOperator._sympy_operator`"""
+        sympy = have_optional_dependency("sympy")
         return sympy.Min(left, right)
 
 
@@ -662,6 +665,7 @@ def _binary_new_copy(self, left, right):
 
     def _sympy_operator(self, left, right):
         """Override :meth:`pybamm.BinaryOperator._sympy_operator`"""
+        sympy = have_optional_dependency("sympy")
         return sympy.Max(left, right)
 
 

pybamm/expression_tree/concatenations.py

@@ -5,10 +5,10 @@
 from collections import defaultdict
 
 import numpy as np
-import sympy
 from scipy.sparse import issparse, vstack
 
 import pybamm
+from pybamm.util import have_optional_dependency
 
 
 class Concatenation(pybamm.Symbol):
@@ -135,6 +135,7 @@ def is_constant(self):
 
     def _sympy_operator(self, *children):
         """Apply appropriate SymPy operators."""
+        sympy = have_optional_dependency("sympy")
         self.concat_latex = tuple(map(sympy.latex, children))
 
         if self.print_name is not None:

pybamm/expression_tree/functions.py

@@ -3,13 +3,11 @@
 #
 import numbers
 
-import autograd
 import numpy as np
-import sympy
 from scipy import special
 
 import pybamm
-
+from pybamm.util import have_optional_dependency
 
 class Function(pybamm.Symbol):
     """
@@ -96,6 +94,7 @@ def _function_diff(self, children, idx):
         Derivative with respect to child number 'idx'.
         See :meth:`pybamm.Symbol._diff()`.
         """
+        autograd = have_optional_dependency("autograd")
         # Store differentiated function, needed in case we want to convert to CasADi
         if self.derivative == "autograd":
             return Function(
@@ -202,6 +201,7 @@ def _sympy_operator(self, child):
 
     def to_equation(self):
         """Convert the node and its subtree into a SymPy equation."""
+        sympy = have_optional_dependency("sympy")
         if self.print_name is not None:
             return sympy.Symbol(self.print_name)
         else:
@@ -250,6 +250,7 @@ def _function_new_copy(self, children):
 
     def _sympy_operator(self, child):
         """Apply appropriate SymPy operators."""
+        sympy = have_optional_dependency("sympy")
         class_name = self.__class__.__name__.lower()
         sympy_function = getattr(sympy, class_name)
         return sympy_function(child)
@@ -267,6 +268,7 @@ def _function_diff(self, children, idx):
 
     def _sympy_operator(self, child):
         """Override :meth:`pybamm.Function._sympy_operator`"""
+        sympy = have_optional_dependency("sympy")
         return sympy.asinh(child)
 
 
@@ -287,6 +289,7 @@ def _function_diff(self, children, idx):
 
     def _sympy_operator(self, child):
         """Override :meth:`pybamm.Function._sympy_operator`"""
+        sympy = have_optional_dependency("sympy")
         return sympy.atan(child)
 
 

pybamm/expression_tree/independent_variable.py

@@ -1,9 +1,8 @@
 #
 # IndependentVariable class
 #
-import sympy
-
 import pybamm
+from pybamm.util import have_optional_dependency
 
 KNOWN_COORD_SYS = ["cartesian", "cylindrical polar", "spherical polar"]
 
@@ -44,6 +43,7 @@ def _jac(self, variable):
 
     def to_equation(self):
         """Convert the node and its subtree into a SymPy equation."""
+        sympy = have_optional_dependency("sympy")
         if self.print_name is not None:
             return sympy.Symbol(self.print_name)
         else:
@@ -77,6 +77,7 @@ def _evaluate_for_shape(self):
 
     def to_equation(self):
         """Convert the node and its subtree into a SymPy equation."""
+        sympy = have_optional_dependency("sympy")
         return sympy.Symbol("t")
 
 

pybamm/expression_tree/operations/latexify.py

@@ -5,10 +5,9 @@
 import re
 import warnings
 
-import sympy
-
 import pybamm
 from pybamm.expression_tree.printing.sympy_overrides import custom_print_func
+from pybamm.util import have_optional_dependency
 
 
 def get_rng_min_max_name(rng, min_or_max):
@@ -88,6 +87,7 @@ def _get_bcs_displays(self, var):
         Returns a list of boundary condition equations with ranges in front of
         the equations.
         """
+        sympy = have_optional_dependency("sympy")
         bcs_eqn_list = []
         bcs = self.model.boundary_conditions.get(var, None)
 
@@ -118,6 +118,7 @@ def _get_bcs_displays(self, var):
 
     def _get_param_var(self, node):
         """Returns a list of parameters and a list of variables."""
+        sympy = have_optional_dependency("sympy")
         param_list = []
         var_list = []
         dfs_nodes = [node]
@@ -160,6 +161,7 @@ def _get_param_var(self, node):
         return param_list, var_list
 
     def latexify(self, output_variables=None):
+        sympy = have_optional_dependency("sympy")
         # Voltage is the default output variable if it exists
         if output_variables is None:
             if "Voltage [V]" in self.model.variables: