A possible solution for allowing custom themes

powerline_shell/__init__.py

@@ -6,7 +6,7 @@ import os
 import sys
 import importlib
 import json
-from .utils import warn, py3
+from .utils import warn, py3, import_file
 import re
 
 
@@ -168,6 +168,23 @@ DEFAULT_CONFIG = {
 }
 
 
+class ThemeNotFoundException(Exception):
+    pass
+
+
+def read_theme(config):
+    theme_name = config.get("theme", "default")
+    try:
+        mod = importlib.import_module("powerline_shell.themes." + theme_name)
+    except ImportError:
+        try:
+            mod = import_file("custom_theme", os.path.expanduser(theme_name))
+        except ImportError:
+            raise ThemeNotFoundException(
+                "Theme " + theme_name + " cannot be found")
+    return getattr(mod, "Color")
+
+
 def main():
     arg_parser = argparse.ArgumentParser()
     arg_parser.add_argument('--generate-config', action='store_true',
@@ -190,9 +207,7 @@ def main():
     else:
         config = DEFAULT_CONFIG
 
-    theme_name = config.get("theme", "default")
-    mod = importlib.import_module("powerline_shell.themes." + theme_name)
-    theme = getattr(mod, "Color")
+    theme = read_theme(config)
 
     powerline = Powerline(args, config, theme)
     segments = []

powerline_shell/utils.py

@@ -98,3 +98,21 @@ class ThreadedSegment(threading.Thread):
     def __init__(self, powerline):
         super(ThreadedSegment, self).__init__()
         self.powerline = powerline
+
+
+def import_file(module_name, path):
+    # An implementation of https://stackoverflow.com/a/67692/683436
+    if py3 and sys.version_info[1] >= 5:
+        import importlib.util
+        spec = importlib.util.spec_from_file_location(module_name, path)
+        if not spec:
+            raise ImportError()
+        mod = importlib.util.module_from_spec(spec)
+        spec.loader.exec_module(mod)
+        return mod
+    elif py3:
+        from importlib.machinery import SourceFileLoader
+        return SourceFileLoader(module_name, path).load_module()
+    else:
+        import imp
+        return imp.load_source(module_name, path)