Add tools/update_toc.py to automatically replace TOC

tools/update_toc.py

@@ -0,0 +1,44 @@
+import re
+from subprocess import check_output
+
+
+def get_new_toc():
+    new_toc = check_output(
+        'markdown-toc README.md',
+        shell=True
+    ).decode('utf-8')
+
+    pattern = ['<!-- toc -->', '', new_toc, '', '<!-- tocstop -->']
+
+    return '\n'.join(pattern)
+
+
+def get_readme():
+    with open('README.md', 'r') as f:
+        return f.read()
+
+
+def save_readme(readme):
+    with open('README.md', 'w') as f:
+        return f.write(readme)
+
+
+def replace_toc():
+    readme = get_readme()
+    new_toc = get_new_toc()
+
+    regex = '<!-- toc -->(.|\n)+<!-- tocstop -->'
+
+    new_readme = re.sub(regex, new_toc, readme)
+
+    save_readme(new_readme)
+
+    print('TOC updated ...')
+
+
+def main():
+    return replace_toc()
+
+
+if __name__ == '__main__':
+    main()