diff --git a/PFERD/temp_folder.py b/PFERD/tmp_dir.py
similarity index 63%
rename from PFERD/temp_folder.py
rename to PFERD/tmp_dir.py
index ad4da67..58706f5 100644
--- a/PFERD/temp_folder.py
+++ b/PFERD/tmp_dir.py
@@ -1,25 +1,24 @@
 """Helper functions and classes for temporary folders."""
 
-from typing import Optional, Type
-from types import TracebackType
-
-import pathlib
 import shutil
+from pathlib import Path
+from types import TracebackType
+from typing import Optional, Type
 
 
-class TempFolder():
+class TmpDir():
     """A temporary folder that can create files or nested temp folders."""
 
-    def __init__(self, path: pathlib.Path):
+    def __init__(self, path: Path):
         """Create a new temporary folder for the given path."""
-        self.counter = 0
-        self.path = path
+        self._counter = 0
+        self._path = path
 
     def __str__(self) -> str:
         """Format the folder as a string."""
         return f"Folder at {self.path}"
 
-    def __enter__(self) -> 'TempFolder':
+    def __enter__(self) -> 'TmpDir':
         """Context manager entry function."""
         return self
 
@@ -31,26 +30,31 @@ class TempFolder():
         self.cleanup()
         return None
 
-    def new_file(self) -> pathlib.Path:
+    @property
+    def path(self) -> Path:
+        """Return the path of this folder."""
+        return self._path
+
+    def new_file(self, prefix: Optional[str] = None) -> Path:
         """Return a unique path inside the folder, but don't create a file."""
-        name = f"tmp-{self.__inc_and_get_counter():03}"
+        name = f"{prefix if prefix else 'tmp'}-{self._inc_and_get_counter():03}"
         return self.path.joinpath(name)
 
-    def new_folder(self, prefix: str = "") -> 'TempFolder':
+    def new_folder(self, prefix: Optional[str] = None) -> 'TmpDir':
         """Create a new nested temporary folder and return its path."""
-        name = f"{prefix if prefix else 'tmp'}-{self.__inc_and_get_counter():03}"
+        name = f"{prefix if prefix else 'tmp'}-{self._inc_and_get_counter():03}"
 
         sub_path = self.path.joinpath(name)
         sub_path.mkdir(parents=True)
 
-        return TempFolder(sub_path)
+        return TmpDir(sub_path)
 
     def cleanup(self) -> None:
         """Delete this folder and all contained files."""
         shutil.rmtree(self.path.absolute())
 
-    def __inc_and_get_counter(self) -> int:
+    def _inc_and_get_counter(self) -> int:
         """Get and increment the counter by one."""
-        counter = self.counter
-        self.counter += 1
+        counter = self._counter
+        self._counter += 1
         return counter