diff --git a/README.md b/README.md
index d680de4..bf68939 100644
--- a/README.md
+++ b/README.md
@@ -4,13 +4,13 @@ PDF pattern generator of AprilTags and AR tags
 * [*PyFPDF*](https://pyfpdf.readthedocs.io/en/latest/index.html)  a library for PDF document generation under Python
 * [*PyYAML*](https://pyyaml.org/)  a full-featured YAML framework for the Python
 ```
-sudo pip install fpdf pyyaml
+sudo pip3 install fpdf pyyaml
 ```
 ## Usage
 * Configuration file [**cfg.yaml**](https://github.com/cgdsss/pattern_generator/blob/master/cfg.yaml)
 * Run scripts
   ```
-  python tag.py
+  python3 tag.py
   ```
 * A pdf file was generated, like [pattern.pdf](https://github.com/cgdsss/pattern_generator/blob/master/pattern.pdf)
 ## Resources
diff --git a/tag.py b/tag.py
index a07e896..9b95764 100644
--- a/tag.py
+++ b/tag.py
@@ -3,7 +3,7 @@
 import os
 
 current_path = os.path.abspath(os.path.dirname(__file__))
-stream = file(os.path.join(current_path, 'cfg.yaml'), 'r')
+stream = open(os.path.join(current_path, 'cfg.yaml'), 'r')
 cfg = yaml.load(stream)
 
 tag_type = cfg['tag_type']
@@ -14,17 +14,17 @@
 
 pdf = FPDF(orientation = 'P', unit = 'cm', format=(pdf_size[0]*100.0, pdf_size[1]*100.0))
 pdf.add_page()
-print "Drawing: "
+print("Drawing: ")
 for i in range(len(tags_id)):
-    print "--"
-    print "id: ", str(tags_id[i])
-    print "size: {0}m".format(tags_size[i])
-    print "position: {0}m, {1}m".format(tags_pose[i][0], tags_pose[i][1])
+    print("--")
+    print("id: ", str(tags_id[i]))
+    print("size: {0}m".format(tags_size[i]))
+    print("position: {0}m, {1}m".format(tags_pose[i][0], tags_pose[i][1]))
     img = os.path.join(current_path, 'png/' + tag_type + "/" + str(tags_id[i]) + ".png")
     pdf.image(img, ((tags_pose[i][0] - tags_size[i] / 2.0) + pdf_size[0]/2.0) * 100.0,
         ((-tags_pose[i][1] - tags_size[i] / 2.0) + pdf_size[1]/2.0) * 100.0,
         tags_size[i] * 100.0, tags_size[i] * 100.0)
 pdf_file = os.path.join(current_path, 'pattern.pdf')
 pdf.output(pdf_file, 'F')
-print "Done."
-print "Already generated:", pdf_file
\ No newline at end of file
+print("Done.")
+print("Already generated:", pdf_file)