Add a helper function sequence_join to join a sequence by a separator

pygmt/helpers/__init__.py

@@ -23,5 +23,6 @@
     is_nonstr_iter,
     launch_external_viewer,
     non_ascii_to_octal,
+    sequence_join,
 )
 from pygmt.helpers.validators import validate_output_table_type

pygmt/helpers/utils.py

@@ -711,3 +711,120 @@ def args_in_kwargs(args: Sequence[str], kwargs: dict[str, Any]) -> bool:
     return any(
         kwargs.get(arg) is not None and kwargs.get(arg) is not False for arg in args
     )
+
+
+def sequence_join(
+    value: Any,
+    separator: str = "/",
+    size: int | Sequence[int] | None = None,
+    ndim: int = 1,
+    name: str | None = None,
+) -> str | list[str] | None | Any:
+    """
+    Join a sequence of values into a string separated by a separator.
+
+    A 1-D sequence will be joined into a single string. A 2-D sequence will be joined
+    into a list of strings. Non-sequence values will be returned as is.
+
+    Parameters
+    ----------
+    value
+        The 1-D or 2-D sequence of values to join.
+    separator
+        The separator to join the values.
+    size
+        Expected size of the 1-D sequence. It can be either an integer or a sequence of
+        integers. If an integer, it is the expected size of the 1-D sequence. If it is a
+        sequence, it is the allowed sizes of the 1-D sequence.
+    ndim
+        The expected maximum number of dimensions of the sequence.
+    name
+        The name of the parameter to be used in the error message.
+
+    Returns
+    -------
+    joined_value
+        The joined string or list of strings.
+
+    Examples
+    --------
+    >>> sequence_join("1/2/3/4")
+    '1/2/3/4'
+    >>> sequence_join(None)
+    >>> sequence_join(True)
+    True
+    >>> sequence_join(False)
+    False
+
+    >>> sequence_join([])
+    Traceback (most recent call last):
+        ...
+    pygmt.exceptions.GMTInvalidInput: Expected a sequence but got an empty sequence.
+
+    >>> sequence_join([1, 2, 3, 4])
+    '1/2/3/4'
+    >>> sequence_join([1, 2, 3, 4], separator=",")
+    '1,2,3,4'
+    >>> sequence_join([1, 2, 3, 4], separator="/", size=4)
+    '1/2/3/4'
+    >>> sequence_join([1, 2, 3, 4], separator="/", size=[2, 4])
+    '1/2/3/4'
+    >>> sequence_join([1, 2, 3, 4], separator="/", size=[2, 4], ndim=2)
+    '1/2/3/4'
+    >>> sequence_join([1, 2, 3, 4], separator="/", size=2)
+    Traceback (most recent call last):
+        ...
+    pygmt.exceptions.GMTInvalidInput: Expected a sequence of 2 values, but got 4 values.
+    >>> sequence_join([1, 2, 3, 4, 5], separator="/", size=[2, 4], name="parname")
+    Traceback (most recent call last):
+        ...
+    pygmt.exceptions.GMTInvalidInput: Parameter 'parname': Expected ...
+
+    >>> sequence_join([[1, 2], [3, 4]], separator="/")
+    Traceback (most recent call last):
+        ...
+    pygmt.exceptions.GMTInvalidInput: Expected a 1-D ..., but a 2-D sequence is given.
+    >>> sequence_join([[1, 2], [3, 4]], separator="/", ndim=2)
+    ['1/2', '3/4']
+    >>> sequence_join([[1, 2], [3, 4]], separator="/", size=2, ndim=2)
+    ['1/2', '3/4']
+    >>> sequence_join([[1, 2], [3, 4]], separator="/", size=4, ndim=2)
+    Traceback (most recent call last):
+        ...
+    pygmt.exceptions.GMTInvalidInput: Expected a sequence of 4 values.
+    >>> sequence_join([[1, 2], [3, 4]], separator="/", size=[2, 4], ndim=2)
+    ['1/2', '3/4']
+    """
+    # Return the original value if it is not a sequence (e.g., None, bool, or str).
+    if not is_nonstr_iter(value):
+        return value
+    # Now it must be a sequence.
+
+    # Change size to a list to simplify the checks.
+    size = [size] if isinstance(size, int) else size
+    errmsg = {
+        "name": f"Parameter '{name}': " if name else "",
+        "sizes": ", ".join(str(s) for s in size) if size is not None else "",
+    }
+
+    if len(value) == 0:
+        msg = f"{errmsg['name']}Expected a sequence but got an empty sequence."
+        raise GMTInvalidInput(msg)
+
+    if not is_nonstr_iter(value[0]):  # 1-D sequence.
+        if size is not None and len(value) not in size:
+            msg = (
+                f"{errmsg['name']}Expected a sequence of {errmsg['sizes']} values, "
+                f"but got {len(value)} values."
+            )
+            raise GMTInvalidInput(msg)
+        return separator.join(str(v) for v in value)
+
+    # Now it must be a 2-D sequence.
+    if ndim == 1:
+        msg = f"{errmsg['name']}Expected a 1-D sequence, but a 2-D sequence is given."
+        raise GMTInvalidInput(msg)
+    if size is not None and any(len(i) not in size for i in value):
+        msg = f"{errmsg['name']}Expected a sequence of {errmsg['sizes']} values."
+        raise GMTInvalidInput(msg)
+    return [separator.join(str(j) for j in sub) for sub in value]

pygmt/src/grdclip.py

@@ -12,100 +12,14 @@
     build_arg_list,
     deprecate_parameter,
     fmt_docstring,
-    is_nonstr_iter,
     kwargs_to_strings,
+    sequence_join,
     use_alias,
 )
 
 __doctest_skip__ = ["grdclip"]
 
 
-def _parse_sequence(name, value, separator="/", size=2, ndim=1):
-    """
-    Parse a 1-D or 2-D sequence of values and join them by a separator.
-
-    Parameters
-    ----------
-    name
-        The parameter name.
-    value
-        The 1-D or 2-D sequence of values to parse.
-    separator
-        The separator to join the values.
-    size
-        The number of values in the sequence.
-    ndim
-        The expected maximum number of dimensions of the sequence.
-
-    Returns
-    -------
-    str
-        The parsed sequence.
-
-    Examples
-    --------
-    >>> _parse_sequence("above_or_below", [1000, 0], size=2, ndim=1)
-    '1000/0'
-    >>> _parse_sequence("between", [1000, 1500, 10000], size=3, ndim=2)
-    '1000/1500/10000'
-    >>> _parse_sequence("between", [[1000, 1500, 10000]], size=3, ndim=2)
-    ['1000/1500/10000']
-    >>> _parse_sequence(
-    ...     "between", [[1000, 1500, 10000], [1500, 2000, 20000]], size=3, ndim=2
-    ... )
-    ['1000/1500/10000', '1500/2000/20000']
-    >>> _parse_sequence("replace", [1000, 0], size=2, ndim=2)
-    '1000/0'
-    >>> _parse_sequence("replace", [[1000, 0]], size=2, ndim=2)
-    ['1000/0']
-    >>> _parse_sequence("replace", [[1000, 0], [1500, 10000]], size=2, ndim=2)
-    ['1000/0', '1500/10000']
-    >>> _parse_sequence("any", "1000/100")
-    '1000/100'
-    >>> _parse_sequence("any", None)
-    >>> _parse_sequence("any", [])
-    []
-    >>> _parse_sequence("above_or_below", [[100, 1000], [1500, 2000]], size=2, ndim=1)
-    Traceback (most recent call last):
-        ...
-    pygmt.exceptions.GMTInvalidInput: Parameter ... must be a 1-D sequence...
-    >>> _parse_sequence("above_or_below", [100, 200, 300], size=2, ndim=1)
-    Traceback (most recent call last):
-    ...
-    pygmt.exceptions.GMTInvalidInput: Parameter ... must be a 1-D sequence ...
-    >>> _parse_sequence("between", [[100, 200, 300], [500, 600]], size=3, ndim=2)
-    Traceback (most recent call last):
-    ...
-    pygmt.exceptions.GMTInvalidInput: Parameter ... must be a 2-D sequence with ...
-    """
-    # Return the value as is if not a sequence (e.g., str or None) or empty.
-    if not is_nonstr_iter(value) or len(value) == 0:
-        return value
-
-    # 1-D sequence
-    if not is_nonstr_iter(value[0]):
-        if len(value) != size:
-            msg = (
-                f"Parameter '{name}' must be a 1-D sequence of {size} values, "
-                f"but got {len(value)} values."
-            )
-            raise GMTInvalidInput(msg)
-        return separator.join(str(i) for i in value)
-
-    # 2-D sequence
-    if ndim == 1:
-        msg = f"Parameter '{name}' must be a 1-D sequence, not a 2-D sequence."
-        raise GMTInvalidInput(msg)
-
-    if any(len(i) != size for i in value):
-        msg = (
-            f"Parameter '{name}' must be a 2-D sequence with each sub-sequence "
-            f"having {size} values."
-        )
-        raise GMTInvalidInput(msg)
-    return [separator.join(str(j) for j in value[i]) for i in range(len(value))]
-
-
 # TODO(PyGMT>=0.19.0): Remove the deprecated "new" parameter.
 @fmt_docstring
 @deprecate_parameter("new", "replace", "v0.15.0", remove_version="v0.19.0")
@@ -198,10 +112,10 @@ def grdclip(
         raise GMTInvalidInput(msg)
 
     # Parse the -S option.
-    kwargs["Sa"] = _parse_sequence("above", above, size=2, ndim=1)
-    kwargs["Sb"] = _parse_sequence("below", below, size=2, ndim=1)
-    kwargs["Si"] = _parse_sequence("between", between, size=3, ndim=2)
-    kwargs["Sr"] = _parse_sequence("replace", replace, size=2, ndim=2)
+    kwargs["Sa"] = sequence_join(above, size=2, name="above")
+    kwargs["Sb"] = sequence_join(below, size=2, name="below")
+    kwargs["Si"] = sequence_join(between, size=3, ndim=2, name="between")
+    kwargs["Sr"] = sequence_join(replace, size=2, ndim=2, name="replace")
 
     with Session() as lib:
         with (