diff --git a/doc/templates.md b/doc/templates.md
index 1eaf6e0..c52a7b7 100644
--- a/doc/templates.md
+++ b/doc/templates.md
@@ -131,3 +131,10 @@ Operations on variables
     if it's empty or non-existing.
 - `$set(name,value)`: set `%name%` to `value`.
 - `$unset(name)`: unset `%name%`.
+
+`$python()`
+-----------
+
+- `$python(expr,imports)`: evaluate an arbitrary python expression `expr`.
+    `imports` is a space-separated list of modules to import (can be omitted).
+
diff --git a/qygmy/templates/functions.py b/qygmy/templates/functions.py
index f6143f1..f0597cb 100644
--- a/qygmy/templates/functions.py
+++ b/qygmy/templates/functions.py
@@ -127,3 +127,11 @@ def context_time(ctx, seconds):
     else:
         return ctx['__timefmt__'][2].format(sign, m, s)
 
+def context_python(ctx, expression, imports=''):
+    modules = {'__builtins__': __builtins__}
+    if imports:
+        for m in imports.split():
+            topname = m.split('.', 1)[0]
+            modules[topname] = __import__(m)
+    return str(eval(expression, modules, ctx))
+