Add the validate_output_table_type function to check the output_type parameter

pygmt/helpers/__init__.py

@@ -21,3 +21,4 @@
     launch_external_viewer,
     non_ascii_to_octal,
 )
+from pygmt.helpers.validators import validate_output_table_type

pygmt/helpers/validators.py

@@ -0,0 +1,41 @@
+"""
+Functions to check if given arguments are valid.
+"""
+import warnings
+
+from pygmt.exceptions import GMTInvalidInput
+
+
+def validate_output_table_type(output_type, outfile=None):
+    """
+    Check if the ``output_type`` and ``outfile`` parameters are valid.
+
+    Parameters
+    ----------
+    output_type : str
+        The type for a table output. Valid values are "file", "numpy", and
+        "pandas".
+    outfile : str
+        The file name for the output table file. Required if
+        ``output_type="file"``.
+
+    Returns
+    -------
+    str
+        The original or corrected output type.
+    """
+    if output_type not in ["file", "numpy", "pandas"]:
+        raise GMTInvalidInput(
+            "Must specify 'output_type' either as 'file', 'numpy', or 'pandas'."
+        )
+    if output_type == "file" and outfile is None:
+        raise GMTInvalidInput("Must specify 'outfile' for output_type='file'.")
+    if output_type != "file" and outfile is not None:
+        msg = (
+            f"Changing 'output_type' from '{output_type}' to 'file' "
+            "since 'outfile' parameter is set. Please use output_type='file' "
+            "to silence this warning."
+        )
+        warnings.warn(message=msg, category=RuntimeWarning, stacklevel=2)
+        output_type = "file"
+    return output_type

pygmt/src/filter1d.py

@@ -1,12 +1,17 @@
 """
 filter1d - Time domain filtering of 1-D data tables
 """
-import warnings
 
 import pandas as pd
 from pygmt.clib import Session
 from pygmt.exceptions import GMTInvalidInput
-from pygmt.helpers import GMTTempFile, build_arg_string, fmt_docstring, use_alias
+from pygmt.helpers import (
+    GMTTempFile,
+    build_arg_string,
+    fmt_docstring,
+    use_alias,
+    validate_output_table_type,
+)
 
 
 @fmt_docstring
@@ -109,18 +114,8 @@ def filter1d(data, output_type="pandas", outfile=None, **kwargs):
     """
     if kwargs.get("F") is None:
         raise GMTInvalidInput("Pass a required argument to 'filter_type'.")
-    if output_type not in ["numpy", "pandas", "file"]:
-        raise GMTInvalidInput("Must specify format as either numpy, pandas, or file.")
-    if outfile is not None and output_type != "file":
-        msg = (
-            f"Changing `output_type` of filter1d from '{output_type}' to 'file' "
-            "since `outfile` parameter is set. Please use `output_type='file'` "
-            "to silence this warning."
-        )
-        warnings.warn(msg, category=RuntimeWarning, stacklevel=2)
-        output_type = "file"
-    elif output_type == "file" and outfile is None:
-        raise GMTInvalidInput("Must specify outfile for ASCII output.")
+
+    output_type = validate_output_table_type(output_type, outfile=outfile)
 
     with GMTTempFile() as tmpfile:
         with Session() as lib:

pygmt/src/grd2xyz.py

@@ -1,7 +1,6 @@
 """
 grd2xyz - Convert grid to data table
 """
-import warnings
 
 import pandas as pd
 import xarray as xr
@@ -13,6 +12,7 @@
     fmt_docstring,
     kwargs_to_strings,
     use_alias,
+    validate_output_table_type,
 )
 
 __doctest_skip__ = ["grd2xyz"]
@@ -143,21 +143,7 @@ def grd2xyz(grid, output_type="pandas", outfile=None, **kwargs):
     0  10.0  25.0      863.0
     1  10.5  25.0      985.5
     """
-    if output_type not in ["numpy", "pandas", "file"]:
-        raise GMTInvalidInput(
-            "Must specify 'output_type' either as 'numpy', 'pandas' or 'file'."
-        )
-
-    if outfile is not None and output_type != "file":
-        msg = (
-            f"Changing 'output_type' of grd2xyz from '{output_type}' to 'file' "
-            "since 'outfile' parameter is set. Please use output_type='file' "
-            "to silence this warning."
-        )
-        warnings.warn(message=msg, category=RuntimeWarning, stacklevel=2)
-        output_type = "file"
-    elif outfile is None and output_type == "file":
-        raise GMTInvalidInput("Must specify 'outfile' for ASCII output.")
+    output_type = validate_output_table_type(output_type, outfile=outfile)
 
     if kwargs.get("o") is not None and output_type == "pandas":
         raise GMTInvalidInput(

pygmt/src/grdhisteq.py

@@ -1,7 +1,6 @@
 """
 grdhisteq - Perform histogram equalization for a grid.
 """
-import warnings
 
 import numpy as np
 import pandas as pd
@@ -13,6 +12,7 @@
     fmt_docstring,
     kwargs_to_strings,
     use_alias,
+    validate_output_table_type,
 )
 from pygmt.io import load_dataarray
 
@@ -321,23 +321,11 @@ def compute_bins(
         This method does a weighted histogram equalization for geographic
         grids to account for node area varying with latitude.
         """
-        # Return a pandas.DataFrame if ``outfile`` is not set
-        if output_type not in ["numpy", "pandas", "file"]:
-            raise GMTInvalidInput(
-                "Must specify 'output_type' either as 'numpy', 'pandas' or 'file'."
-            )
+        output_type = validate_output_table_type(output_type, outfile=outfile)
 
         if header is not None and output_type != "file":
             raise GMTInvalidInput("'header' is only allowed with output_type='file'.")
 
-        if isinstance(outfile, str) and output_type != "file":
-            msg = (
-                f"Changing 'output_type' from '{output_type}' to 'file' "
-                "since 'outfile' parameter is set. Please use output_type='file' "
-                "to silence this warning."
-            )
-            warnings.warn(message=msg, category=RuntimeWarning, stacklevel=2)
-            output_type = "file"
         with GMTTempFile(suffix=".txt") as tmpfile:
             if output_type != "file":
                 outfile = tmpfile.name

pygmt/src/grdvolume.py

@@ -3,13 +3,13 @@
 """
 import pandas as pd
 from pygmt.clib import Session
-from pygmt.exceptions import GMTInvalidInput
 from pygmt.helpers import (
     GMTTempFile,
     build_arg_string,
     fmt_docstring,
     kwargs_to_strings,
     use_alias,
+    validate_output_table_type,
 )
 
 __doctest_skip__ = ["grdvolume"]
@@ -101,12 +101,7 @@ def grdvolume(grid, output_type="pandas", outfile=None, **kwargs):
     3  350  2.018302e+12  5.222640e+14  258.764032
     4  400  1.857370e+12  4.252699e+14  228.963499
     """
-    if output_type not in ["numpy", "pandas", "file"]:
-        raise GMTInvalidInput(
-            """Must specify format as either numpy, pandas, or file."""
-        )
-    if output_type == "file" and outfile is None:
-        raise GMTInvalidInput("""Must specify outfile for ASCII output.""")
+    output_type = validate_output_table_type(output_type, outfile=outfile)
 
     with GMTTempFile() as tmpfile:
         with Session() as lib:

pygmt/src/triangulate.py

@@ -2,7 +2,6 @@
 triangulate - Delaunay triangulation or Voronoi partitioning and gridding of
 Cartesian data.
 """
-import warnings
 
 import pandas as pd
 from pygmt.clib import Session
@@ -13,6 +12,7 @@
     fmt_docstring,
     kwargs_to_strings,
     use_alias,
+    validate_output_table_type,
 )
 from pygmt.io import load_dataarray
 
@@ -357,20 +357,7 @@ def delaunay_triples(  # pylint: disable=too-many-arguments,too-many-locals
         ``triangulate`` is a Cartesian or small-geographic area operator and is
         unaware of periodic or polar boundary conditions.
         """
-        # Return a pandas.DataFrame if ``outfile`` is not set
-        if output_type not in ["numpy", "pandas", "file"]:
-            raise GMTInvalidInput(
-                "Must specify 'output_type' either as 'numpy', 'pandas' or 'file'."
-            )
-
-        if isinstance(outfile, str) and output_type != "file":
-            msg = (
-                f"Changing 'output_type' from '{output_type}' to 'file' "
-                "since 'outfile' parameter is set. Please use output_type='file' "
-                "to silence this warning."
-            )
-            warnings.warn(message=msg, category=RuntimeWarning, stacklevel=2)
-            output_type = "file"
+        output_type = validate_output_table_type(output_type, outfile)
 
         # Return a pandas.DataFrame if ``outfile`` is not set
         with GMTTempFile(suffix=".txt") as tmpfile: