Figure.grdcontour: Adjust processing of arguments passed to the "annotation" and "interval" parameters, deprecate "sequence_plus"

pygmt/src/grdcontour.py

@@ -2,8 +2,16 @@
 grdcontour - Plot a contour figure.
 """
 
+import warnings
+
 from pygmt.clib import Session
-from pygmt.helpers import build_arg_list, fmt_docstring, kwargs_to_strings, use_alias
+from pygmt.helpers import (
+    build_arg_list,
+    fmt_docstring,
+    is_nonstr_iter,
+    kwargs_to_strings,
+    use_alias,
+)
 
 __doctest_skip__ = ["grdcontour"]
 
@@ -27,9 +35,7 @@
     p="perspective",
     t="transparency",
 )
-@kwargs_to_strings(
-    R="sequence", L="sequence", A="sequence_plus", c="sequence_comma", p="sequence"
-)
+@kwargs_to_strings(R="sequence", L="sequence", c="sequence_comma", p="sequence")
 def grdcontour(self, grid, **kwargs):
     r"""
     Convert grids or images to contours and plot them on maps.
@@ -43,26 +49,26 @@ def grdcontour(self, grid, **kwargs):
     Parameters
     ----------
     {grid}
-    interval : str or int
+    interval : float, list, or str
         Specify the contour lines to generate.
 
-        - The file name of a CPT file where the color boundaries will
-          be used as contour levels.
-        - The file name of a 2 (or 3) column file containing the contour
-          levels (col 1), (**C**)ontour or (**A**)nnotate (col 2), and optional
-          angle (col 3).
-        - A fixed contour interval *cont_int* or a single contour with
-          +\ *cont_int*.
-    annotation : str, int, or list
+        - The file name of a CPT file where the color boundaries will be used as
+          contour levels.
+        - The file name of a 2 (or 3) column file containing the contour levels (col 0),
+          (**C**)ontour or (**A**)nnotate (col 1), and optional angle (col 2).
+        - A fixed contour interval.
+        - A list of contour levels.
+    annotation : float, list, or str
         Specify or disable annotated contour levels, modifies annotated
         contours specified in ``interval``.
 
-        - Specify a fixed annotation interval *annot_int* or a
-          single annotation level +\ *annot_int*.
-        - Disable all annotation with  **-**.
-        - Optional label modifiers can be specified as a single string
-          ``"[annot_int]+e"``  or with a list of arguments
-          ``([annot_int], "e", "f10p", "gred")``.
+        - Specify a fixed annotation interval.
+        - Specify a list of annotation levels.
+        - Disable all annotations by setting ``annotation="n"``.
+        - Adjust the appearance by appending different modifiers, e.g.,
+          ``"annot_int+f10p+gred"`` gives annotations with a font size of 10 points
+          and a red filled box. For all available modifiers see
+          :gmt-docs:`grdcontour.html#a`.
     limit : str or list of 2 ints
         *low*/*high*.
         Do no draw contours below `low` or above `high`, specify as string
@@ -96,32 +102,58 @@ def grdcontour(self, grid, **kwargs):
     Example
     -------
     >>> import pygmt
-    >>> # load the 15 arc-minutes grid with "gridline" registration
-    >>> # in a specified region
+    >>> # Load the 15 arc-minutes grid with "gridline" registration in the
+    >>> # specified region
     >>> grid = pygmt.datasets.load_earth_relief(
     ...     resolution="15m",
     ...     region=[-92.5, -82.5, -3, 7],
     ...     registration="gridline",
     ... )
-    >>> # create a new plot with pygmt.Figure()
+    >>> # Create a new plot with pygmt.Figure()
     >>> fig = pygmt.Figure()
-    >>> # create the contour plot
+    >>> # Create the contour plot
     >>> fig.grdcontour(
-    ...     # pass in the grid downloaded above
+    ...     # Pass in the grid downloaded above
     ...     grid=grid,
-    ...     # set the interval for contour lines at 250 meters
+    ...     # Set the interval for contour lines at 250 meters
     ...     interval=250,
-    ...     # set the interval for annotated contour lines at 1,000 meters
+    ...     # Set the interval for annotated contour lines at 1,000 meters
     ...     annotation=1000,
-    ...     # add a frame for the plot
+    ...     # Add a frame for the plot
     ...     frame="a",
-    ...     # set the projection to Mercator for the 10 cm figure
+    ...     # Set the projection to Mercator for the 10 cm figure
     ...     projection="M10c",
     ... )
-    >>> # show the plot
+    >>> # Show the plot
     >>> fig.show()
     """
     kwargs = self._preprocess(**kwargs)
+
+    # Backward compatibility with the old syntax for the annotation parameter, e.g.,
+    # [100, "e", "f10p", "gred"].
+    if is_nonstr_iter(kwargs.get("A")) and any(
+        i[0] in "acdefgijlLnoprtuvwx=" for i in kwargs["A"] if isinstance(i, str)
+    ):
+        msg = (
+            "Argument of the parameter 'annotation'/'A' is using the old, deprecated "
+            "syntax. Please refer to the PyGMT documentation for the new syntax. "
+            "The warning will be removed in v0.14.0 and the old syntax will no longer "
+            "be supported. "
+        )
+        warnings.warn(msg, category=FutureWarning, stacklevel=2)
+        kwargs["A"] = "+".join(f"{item}" for item in kwargs["A"])
+
+    # Specify levels for the annotation and interval parameters.
+    # One level is converted to a string with a trailing comma to separate it from
+    # specifying an interval.
+    # Multiple levels are concatenated to a comma-separated string.
+    for arg in ["A", "C"]:
+        if is_nonstr_iter(kwargs.get(arg)):
+            if len(kwargs[arg]) == 1:  # One level
+                kwargs[arg] = str(kwargs[arg][0]) + ","
+            else:  # Multiple levels
+                kwargs[arg] = ",".join(f"{item}" for item in kwargs[arg])
+
     with Session() as lib:
         with lib.virtualfile_in(check_kind="raster", data=grid) as vingrd:
             lib.call_module(

pygmt/tests/baseline/test_grdcontour_multiple_levels.png.dvc

@@ -0,0 +1,6 @@
+outs:
+- md5: 4d20cdb71af2e6568f64f0246ec860ea
+  size: 64008
+  isexec: true
+  hash: md5
+  path: test_grdcontour_multiple_levels.png

pygmt/tests/baseline/test_grdcontour_one_level.png.dvc

@@ -0,0 +1,6 @@
+outs:
+- md5: fc624766f0b8eac8206735a05c7c9662
+  size: 45023
+  isexec: true
+  hash: md5
+  path: test_grdcontour_one_level.png

pygmt/tests/test_grdcontour.py

@@ -24,7 +24,8 @@ def fixture_grid():
 @pytest.mark.mpl_image_compare
 def test_grdcontour(grid):
     """
-    Plot a contour image using an xarray grid with fixed contour interval.
+    Plot a contour image using an xarray grid with fixed (different) contour and
+    annotation intervals.
     """
     fig = Figure()
     fig.grdcontour(
@@ -33,6 +34,53 @@ def test_grdcontour(grid):
     return fig
 
 
+@pytest.mark.mpl_image_compare
+def test_grdcontour_one_level(grid):
+    """
+    Plot a contour image using an xarray grid with one contour level and one
+    (different) annotation level.
+    """
+    fig = Figure()
+    fig.grdcontour(
+        grid=grid, interval=[400], annotation=[570], projection="M10c", frame=True
+    )
+    return fig
+
+
+@pytest.mark.mpl_image_compare(filename="test_grdcontour_one_level.png")
+def test_grdcontour_old_annotations(grid):
+    """
+    Test the old syntax for the annotation parameter using "sequence_plus".
+    Modified from the "test_grdcontour_one_level()" test. Can be removed in v0.14.0.
+    """
+    fig = Figure()
+    fig.grdcontour(
+        grid=grid,
+        interval=[400],
+        annotation=["570,", "gwhite"],
+        projection="M10c",
+        frame=True,
+    )
+    return fig
+
+
+@pytest.mark.mpl_image_compare
+def test_grdcontour_multiple_levels(grid):
+    """
+    Plot a contour image using an xarray grid with multiple (different) contour
+    and annotation levels.
+    """
+    fig = Figure()
+    fig.grdcontour(
+        grid=grid,
+        interval=[400, 450, 500],
+        annotation=[400, 570],
+        projection="M10c",
+        frame=True,
+    )
+    return fig
+
+
 @pytest.mark.benchmark
 @pytest.mark.mpl_image_compare
 def test_grdcontour_labels(grid):