utils: port csv_dequote.pl to Python

utils/csv_dequote.py

@@ -0,0 +1,91 @@
+#!/usr/bin/env python3
+"""csv_dequote.py.
+
+Take a .csv file with quoted strings, convert the real comma delimiters
+to pipes (|) and strip away the double quote chars.
+
+Author:   Hamish Bowman, Dunedin, New Zealand, June 2012 (original Perl)
+          Python port: 2026
+          (c) 2012 M. Hamish Bowman, and the GRASS Development Team
+License:  GNU GPL >=2. See the GPL.TXT file which comes with GRASS
+          for details.
+
+USAGE:  csv_dequote.py infile.csv [outfile.psv]
+
+  if outfile is not given it will take the basename of the input
+  file and give it the .psv extension ('Pipe Sep Vars').
+"""
+
+import csv
+import os
+import sys
+
+OUTSEP = "|"
+
+
+def main(argv):
+    if len(argv) < 2 or len(argv) > 3:
+        sys.stderr.write("USAGE: csv_dequote.py infile.csv [outfile.psv]\n")
+        return 1
+
+    infile = argv[1]
+    outfile = argv[2] if len(argv) == 3 else None
+
+    if outfile is None:
+        # Match the Perl behavior: File::Basename::fileparse + "$file.psv"
+        # drops the directory component.
+        base = os.path.basename(infile)
+        base_no_ext, _ = os.path.splitext(base)
+        outfile = base_no_ext + ".psv"
+
+    try:
+        fin = open(infile, newline="")
+    except OSError as exc:
+        sys.stderr.write("{}: {}\n".format(infile, exc.strerror))
+        return 1
+
+    try:
+        # "x" creates the file atomically and fails if it already exists,
+        # so we never overwrite an existing file (no check-then-open race).
+        fout = open(outfile, "x", newline="")
+    except FileExistsError:
+        fin.close()
+        sys.stderr.write(
+            'ERROR: "{}" already exists.\n'
+            "       Will not overwrite; aborting.\n".format(outfile)
+        )
+        return 1
+    except OSError as exc:
+        fin.close()
+        sys.stderr.write("{}: {}\n".format(outfile, exc.strerror))
+        return 1
+
+    had_parse_error = False
+    try:
+        reader = csv.reader(fin)
+        # csv.Error is raised by next() on parse failures, not by the writes.
+        # Drive the reader explicitly so we can catch and continue per row.
+        while True:
+            try:
+                row = next(reader)
+            except StopIteration:
+                break
+            except csv.Error as exc:
+                sys.stderr.write(
+                    "Unable to parse CSV at line {} in {}: {}\n".format(
+                        reader.line_num, infile, exc
+                    )
+                )
+                had_parse_error = True
+                continue
+            fout.write(OUTSEP.join(row))
+            fout.write("\n")
+    finally:
+        fin.close()
+        fout.close()
+
+    return 1 if had_parse_error else 0
+
+
+if __name__ == "__main__":
+    sys.exit(main(sys.argv))