Add %pythonbegin directive.

For adding code at the beginning of the generated .py file.

Doc/Manual/Python.html

@@ -3314,6 +3314,53 @@ what can be done without having to rely on any of the more advanced
 customization features.
 </p>
 
+<p>
+There is also <tt>%pythonbegin</tt> which is another directive very similar to <tt>%pythoncode</tt>,
+but generates the given Python code at the beginning of the <tt>.py</tt> file.
+This directive works in the same way as <tt>%pythoncode</tt>, except the code is copied
+just after the SWIG banner (comment) at the top of the file, before any real code.
+This provides an opportunity to add your own description in a comment near the top of the file as well
+as Python imports that have to appear at the top of the file, such as "<tt>from __future__ import</tt>"
+statements.
+</p>
+
+<p>
+The following shows example usage for Python 2.6 to use <tt>print</tt> as it can in Python 3, that is, as a function instead of a statement:
+</p>
+
+<div class="code">
+<pre>
+%pythonbegin %{
+# This module provides wrappers to the Whizz Bang library
+%}
+
+%pythonbegin %{
+from __future__ import print_function
+print("Loading", "Whizz", "Bang", sep=' ... ')
+%}
+</pre>
+</div>
+
+<p>
+which can be seen when viewing the first few lines of the generated <tt>.py</tt> file:
+</p>
+
+<div class="code">
+<pre>
+# This file was automatically generated by SWIG (http://www.swig.org).
+# Version 2.0.11
+#
+# Do not make changes to this file unless you know what you are doing--modify
+# the SWIG interface file instead.
+
+# This module provides wrappers to the Whizz Bang library
+
+from __future__ import print_function
+print("Loading", "Whizz", "Bang", sep=' ... ')
+
+</pre>
+</div>
+
 <p>Sometimes you may want to replace or modify the wrapper function
 that SWIG creates in the proxy <tt>.py</tt> file.  The Python module
 in SWIG provides some features that enable you to do this.  First, to