diff --git a/.gitignore b/.gitignore
index f8b73e7..29dba5a 100644
--- a/.gitignore
+++ b/.gitignore
@@ -137,4 +137,3 @@ dmypy.json
 
 # Cython debug symbols
 cython_debug/
-
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
new file mode 100644
index 0000000..bd8fe37
--- /dev/null
+++ b/.pre-commit-config.yaml
@@ -0,0 +1,27 @@
+---
+default_language_version:
+  python: python3.8
+repos:
+  - repo: https://github.com/psf/black
+    rev: 20.8b1
+    hooks:
+      - id: black
+  - repo: https://github.com/pre-commit/pre-commit-hooks
+    rev: v3.4.0
+    hooks:
+      - id: check-added-large-files
+      - id: check-merge-conflict
+      - id: debug-statements
+      - id: end-of-file-fixer
+      - id: fix-encoding-pragma
+      - id: trailing-whitespace
+      - id: name-tests-test
+        exclude: tests/(common.py|util.py|(helpers|integration/factories)/(.+).py)
+  - repo: https://github.com/asottile/reorder_python_imports
+    rev: v2.4.0
+    hooks:
+      - id: reorder-python-imports
+  - repo: https://github.com/pre-commit/mirrors-mypy
+    rev: v0.800
+    hooks:
+      - id: mypy
diff --git a/README.md b/README.md
index fa8f82a..b6fd780 100644
--- a/README.md
+++ b/README.md
@@ -1,3 +1,3 @@
 # paddy-files
 
-Zero-padding numeric filenames
\ No newline at end of file
+Zero-padding numeric filenames
diff --git a/paddy b/paddy
new file mode 100755
index 0000000..4e10a92
--- /dev/null
+++ b/paddy
@@ -0,0 +1,128 @@
+#! /usr/bin/env python3
+# -*- coding: utf-8 -*-
+import argparse
+import re
+from pathlib import Path
+from typing import List
+from typing import Optional
+
+
+num_matcher = re.compile(r"([0-9]+)")
+
+
+def extract_numbers(s: str) -> str:
+    number_match = num_matcher.search(s)
+    if number_match:
+        return number_match.group(1)
+    return ""
+
+
+def calc_pad_length(files: List[Path]) -> int:
+    max_len = 0
+    for f in files:
+        numbers = extract_numbers(f.name)
+        max_len = max(len(numbers), max_len)
+    return max_len
+
+
+def parse_args() -> argparse.Namespace:
+    parser = argparse.ArgumentParser(
+        description="Pads numbers in file names so they consistently align and sort"
+    )
+    parser.add_argument("files", nargs="+", metavar="file", help="Files to be renamed")
+    parser.add_argument(
+        "-l",
+        "--length",
+        type=int,
+        help="Length of numbers after padding (default: auto)",
+    )
+    parser.add_argument(
+        "-f",
+        "--force",
+        action="store_true",
+        help="Force rename, even if file at destination exists",
+    )
+    parser.add_argument(
+        "-v", "--verbose", action="store_true", help="Print all actions"
+    )
+    parser.add_argument(
+        "-d",
+        "--dry-run",
+        action="store_true",
+        help="Print actions only without modifying any file. Implies --verbose",
+    )
+    parser.add_argument(
+        "-i",
+        "--ignore",
+        metavar="REGEX",
+        help="Regular expression used to ignore files matching the name",
+    )
+    parser.add_argument(
+        "--ignore-files",
+        nargs="+",
+        metavar="IGNOREFILE",
+        help="Files to ignore for renaming. Must add -- before positional arguments",
+    )
+    args = parser.parse_args()
+
+    # Dry run implies verbose
+    if args.dry_run:
+        args.verbose = True
+
+    return args
+
+
+def main() -> int:
+    args = parse_args()
+
+    # Compile ignore pattern, if provided
+    ignore_matcher: Optional[re.Pattern] = None
+    if args.ignore:
+        ignore_matcher = re.compile(args.ignore)
+
+    # Build list of files to act on
+    p = Path(".")
+    files = []
+    for f in args.files:
+        if args.ignore_files and f in args.ignore_files:
+            continue
+        if ignore_matcher and ignore_matcher.match(f):
+            continue
+        files.append(p / f)
+
+    pad_len = args.length
+    if pad_len is None:
+        pad_len = calc_pad_length(files)
+
+    if args.verbose:
+        print(f"Padding to {pad_len}")
+
+    status = 0
+    for f in files:
+        numbers = extract_numbers(f.name)
+        if len(numbers) == pad_len:
+            if args.verbose:
+                print(f"{f.name} is already padded.")
+            continue
+
+        # Pad number and get destination path
+        new_numbers = numbers.zfill(pad_len)
+        new_name = num_matcher.sub(new_numbers, f.name, count=1)
+        new_file = f.parent / new_name
+
+        # Possibly rename unless exists or forced
+        if not new_file.exists() or args.force:
+            if args.verbose:
+                print(f"Rename {f.name} to {new_file.name}")
+            f.rename(new_file)
+        else:
+            print(
+                f"Could not ename {f.name} to {new_file.name}. Destination file exists."
+            )
+            status = 1
+
+    return status
+
+
+if __name__ == "__main__":
+    exit(main())