#38: generate a WfInstance from a .dot file

README.md

@@ -72,6 +72,13 @@ Then you can install pygraphviz by running:
 python3 -m pip install pygraphviz
 ```
 
+#### pydot
+WfCommons uses _pydot_ for reading and writing DOT files. If you want to enable
+this feature, you will have to install the pydot package:
+```
+python3 -m pip install pydot
+```
+
 ## Get in Touch
 
 The main channel to reach the WfCommons team is via the support email: 

wfcommons/common/workflow.py

@@ -9,6 +9,7 @@
 # (at your option) any later version.
 
 import getpass
+import importlib
 import json
 import networkx as nx
 import pathlib
@@ -181,6 +182,12 @@ def read_dot(self, dot_file_path: Optional[pathlib.Path] = None) -> None:
         """
         if not dot_file_path:
             raise FileNotFoundError(f"Not able to find the dot file: {dot_file_path}.")
+
+        graphviz_found = importlib.util.find_spec('pydot')
+        if graphviz_found is None:
+            raise ModuleNotFoundError(
+                f"\'pydot\' package not found: call to {type(self).__name__}.read_dot() failed.")
+
         graph = nx.drawing.nx_pydot.read_dot(dot_file_path)
 
         tasks_map = {}