Refactor to use Session.virtualfile_in and StringIO context manager

Author: seisman

pygmt/src/paragraph.py

@@ -33,13 +33,15 @@ def _parse_font_angle_justify(
     '+a45'
     >>> _parse_font_angle_justify(None, None, "CM")
     '+jCM'
+    >>> _parse_font_angle_justify("10p", 45, None)
+    '+f10p+a45'
     >>> _parse_font_angle_justify("10p,Helvetica-Bold", 45, "CM")
     '+f10p,Helvetica-Bold+a45+jCM'
     """
-    args = ((font, "+f"), (angle, "+a"), (justify, "+j"))
-    if all(arg is None for arg, _ in args):
+    args = {"+f": font, "+a": angle, "+j": justify}
+    if all(arg is None for arg in args.values()):
         return None
-    return "".join(f"{flag}{arg}" for arg, flag in args if arg is not None)
+    return "".join(f"{prefix}{arg}" for prefix, arg in args.items() if arg is not None)
 
 
 def paragraph(
@@ -62,8 +64,8 @@ def paragraph(
     x/y
         The x, y coordinates of the paragraph.
     text
-        The paragraph text to typeset. If a sequence of strings is provided, each
-        string is treated as a separate paragraph.
+        The paragraph text to typeset. If a sequence of strings is provided, each string
+        is treated as a separate paragraph.
     parwidth
         The width of the paragraph.
     linespacing
@@ -91,23 +93,19 @@ def paragraph(
     confdict = {}
     # Prepare the keyword dictionary for the module options
     kwdict = {"M": True, "F": _parse_font_angle_justify(font, angle, justify)}
-
-    # Initialize a stringio object for storing the input data.
-    stringio = io.StringIO()
-    # The header line.
-    stringio.write(f"> {x} {y} {linespacing} {parwidth} {alignment[0]}\n")
-    # The text string to be written to the stringio object.
+    # Prepare the text string that will be passed to an io.StringIO object.
     # Multiple paragraphs are separated by a blank line "\n\n".
     _textstr: str = "\n\n".join(text) if is_nonstr_iter(text) else str(text)
     # Check the encoding of the text string and convert it to octal if necessary.
     if (encoding := _check_encoding(_textstr)) != "ascii":
         _textstr = non_ascii_to_octal(_textstr, encoding=encoding)
         confdict["PS_CHAR_ENCODING"] = encoding
-    # Write the text string to the stringio object.
-    stringio.write(_textstr)
 
     with Session() as lib:
-        with lib.virtualfile_from_stringio(stringio) as vfile:
-            lib.call_module(
-                "text", args=build_arg_list(kwdict, infile=vfile, confdict=confdict)
-            )
+        with io.StringIO() as buffer:  # Prepare the StringIO input.
+            buffer.write(f"> {x} {y} {linespacing} {parwidth} {alignment[0]}\n")
+            buffer.write(_textstr)
+            with lib.virtualfile_in(data=buffer) as vfile:
+                lib.call_module(
+                    "text", args=build_arg_list(kwdict, infile=vfile, confdict=confdict)
+                )