ENH: Add tool to check for deprecated escaped characters.

Python 3.6 deprecates a number of escaped characters that were accepted
before. For instance, '\(' was previously accepted but must now be
written as '\\(' or r'\('.

[ci skip]

1 files changed, 69 insertions, 0 deletions

diff --git a/tools/find_deprecated_escaped_characters.py b/tools/find_deprecated_escaped_characters.py
new file mode 100644
index 000000000..8015d3a42
--- /dev/null
+++ b/tools/find_deprecated_escaped_characters.py
@@ -0,0 +1,69 @@
+#! /usr/bin/env python
+"""
+Look for escape sequences deprecated in Python 3.6.
+
+Python 3.6 deprecates a number of non-escape sequences starting with `\` that
+were accepted before. For instance, '\(' was previously accepted but must now
+be written as '\\(' or r'\('.
+
+"""
+from __future__ import division, absolute_import, print_function
+
+import sys
+
+def main(root):
+    """Find deprecated escape sequences.
+
+    Checks for deprecated escape sequences in ``*.py files``. If `root` is a
+    file, that file is checked, if `root` is a directory all ``*.py`` files
+    found in a recursive descent are checked.
+
+    If a deprecated escape sequence is found, the file and line where found is
+    printed. Note that for multiline strings the line where the string ends is
+    printed and the error(s) are somewhere in the body of the string.
+
+    Parameters
+    ----------
+    root : str
+        File or directory to check.
+    Returns
+    -------
+    None
+
+    """
+    count = 0
+
+    if sys.version_info[:2] >= (3, 6):
+        import ast
+        import tokenize
+        import warnings
+        from pathlib import Path
+
+        base = Path(root)
+        paths = base.rglob("*.py") if base.is_dir() else [base]
+        for path in paths:
+            # use tokenize to auto-detect encoding on systems where no
+            # default encoding is defined (e.g. LANG='C')
+            with tokenize.open(str(path)) as f:
+                with warnings.catch_warnings(record=True) as w:
+                    warnings.simplefilter('always')
+                    tree = ast.parse(f.read())
+                if w:
+                    print("file: ", str(path))
+                    for e in w:
+                        print('line: ', e.lineno, ': ', e.message)
+                    print()
+                    count += len(w)
+    else:
+        raise RuntimeError("Python version must be >= 3.6")
+
+    print("Errors Found", count)
+
+
+if __name__ == "__main__":
+    from argparse import ArgumentParser
+
+    parser = ArgumentParser(description="Find deprecated escaped characters")
+    parser.add_argument('root', help='directory or file to be checked')
+    args = parser.parse_args()
+    main(args.root)