diff --git a/AveryLabels.py b/AveryLabels.py
index fea8374..27c2b3d 100644
--- a/AveryLabels.py
+++ b/AveryLabels.py
@@ -105,7 +105,8 @@ class AveryLabel:
         """ render loop"""
         assert callable(thing) or isinstance(thing, str)
         if isinstance(count, Iterator):
-            return self.render_iterator(thing, count)
+            self.render_iterator(thing, count)
+            return
 
         canv = self.canvas
         for i in range(offset + count):
diff --git a/Dockerfile b/Dockerfile
new file mode 100644
index 0000000..c443dc3
--- /dev/null
+++ b/Dockerfile
@@ -0,0 +1,15 @@
+FROM python:3
+
+WORKDIR /asn-gen
+
+COPY requirements.txt ./
+RUN pip install --no-cache-dir -r requirements.txt
+
+COPY . .
+
+VOLUME ["/out"] 
+
+CMD [ "python", "./asn-gen.py"]
+
+
+# docker exec -it $(docker run -d --rm debian:unstable bash -c "apt-get update && apt-get upgrade -y && sleep 86400") bash
diff --git a/README.md b/README.md
index 8efb2c7..bf5e635 100644
--- a/README.md
+++ b/README.md
@@ -33,12 +33,12 @@ Besides generating ASN labels with a QR Code the tool can also
     ![Label with highlight bar](docs/label-with-hbar.png)
 
 
-### Example usage of ASN with colors:
+### Example usage of ASN labels with colors:
 
 | number ranges | Meaning                                | Color      |
 | ------------ | --------------------------------------- | ---------- |
 | 000000       | Me - normal docs (shorter term storage) | blue       |
-| 100000       | Me - imporatant / (long term storage)   | blue/red   |
+| 100000       | Me - imporatant  (long term storage)    | blue/red   |
 | 200000       | Wife - normal                           | green      |
 | 300000       | Wife - important                        | green/red  |
 | 400000       | Child 1 - normal                        | yellow     |
@@ -62,6 +62,7 @@ Other Avery (or competitor's) label sizes can be added to `labelInfo` in `AveryL
 
 
 ```
+$ ./asn-gen.py -h
 Usage: asn-gen.py [OPTIONS] [filename]
 
 ASN Label Generator
@@ -100,7 +101,7 @@ _**Recommendation:** do test prints on normal paper before printing to the actua
 
 _**Note**: Make sure to set print size to 100%, not fit to page or similar._
 
-### Running the program
+### Running the program from CLI
 Depending on your configuration either use
 
 `` ./asn-gen.py ... ``
@@ -109,6 +110,10 @@ or
 
 `` python3 asn-gen.py ... ``
 
+### Running the program from Docker
+
+
+
 ### Output Filename
 If the filename is omitted the output defaults to
 
diff --git a/asn-gen.py b/asn-gen.py
index 038e484..9a2edd6 100755
--- a/asn-gen.py
+++ b/asn-gen.py
@@ -2,6 +2,7 @@
 
 from functools import partial
 
+import os
 
 from reportlab.lib.units import mm
 from reportlab.lib.units import toLength
@@ -21,6 +22,8 @@ PROJECT_HOMEPAGE = "https://github.com/aborelis/ASN-Label-Generator"
 
 
 class LabelContext:
+
+    """helper class to store context """
     
     # pylint: disable=too-many-instance-attributes
     
@@ -129,6 +132,13 @@ def render(context: LabelContext, c: canvas.Canvas, width: float, height: float)
             c.restoreState()
 
 
+def gen_filename(parm):
+    """generates filename from parameters"""
+    return '-'.join(['label',
+                     str(parm["labeltype"]), parm["prefix"],
+                     str(parm["first_asn"]).zfill(parm["num_digits"]),
+                     str(parm["first_asn"] + parm["number"]).zfill(parm["num_digits"])
+                     ])+'.pdf'
 
 
 def generate(
@@ -155,7 +165,7 @@ def generate(
      # pylint: disable=unused-argument
     """ASN Label Generator
 
-    :param filename: output filename of PDF file generated
+    :param filename: output filename of PDF file generated, if .pdf extension is missing the string will be used as directory
     :param labeltype: Type of label, e.g. 4731, get a list of supported labels with --labels
     :param number: number of labels to generate
 
@@ -193,14 +203,11 @@ def generate(
     parm["labeltype"] = int(parm["labeltype"])
 
     if parm["filename"] is None:
-        parm["filename"] = (
-            "label-"
-            + str(parm["labeltype"])+ "-"
-            + parm["prefix"]+ "-"
-            + str(parm["first_asn"]).zfill(parm["num_digits"])+ "-"
-            + str(parm["first_asn"] + parm["number"]).zfill(parm["num_digits"])
-            + ".pdf"
-        )
+        parm["filename"] = gen_filename(parm)
+    elif not parm["filename"].endswith(".pdf"):
+        parm["filename"] = os.path.join(parm["filename"], gen_filename(parm))
+
+        
 
     context = LabelContext(parm)