diff --git a/doc/Section_python.html b/doc/Section_python.html
index 705538c9a4..42898d7bbf 100644
--- a/doc/Section_python.html
+++ b/doc/Section_python.html
@@ -114,6 +114,11 @@ check which version of Python you have installed, by simply typing
 
 <A NAME = "py_2"></A><H4>11.2 Overview of using Python from a LAMMPS script 
 </H4>
+<P>IMPORTANT NOTE: It is not currently possible to use the
+<A HREF = "python.html">python</A> command described in this section with Python 3,
+only with Python 2.  The C API changed from Python 2 to 3 and the
+LAMMPS code is not compatible with both.
+</P>
 <P>LAMMPS has a <A HREF = "python.html">python</A> command which can be used in an
 input script to define and execute a Python function that you write
 the code for.  The Python function can also be assigned to a LAMMPS
diff --git a/doc/Section_python.txt b/doc/Section_python.txt
index ae256476be..75d654c60f 100644
--- a/doc/Section_python.txt
+++ b/doc/Section_python.txt
@@ -110,6 +110,11 @@ check which version of Python you have installed, by simply typing
 
 11.2 Overview of using Python from a LAMMPS script :link(py_2),h4
 
+IMPORTANT NOTE: It is not currently possible to use the
+"python"_python.html command described in this section with Python 3,
+only with Python 2.  The C API changed from Python 2 to 3 and the
+LAMMPS code is not compatible with both.
+
 LAMMPS has a "python"_python.html command which can be used in an
 input script to define and execute a Python function that you write
 the code for.  The Python function can also be assigned to a LAMMPS
diff --git a/doc/python.html b/doc/python.html
index caea4dfe96..02193dd770 100644
--- a/doc/python.html
+++ b/doc/python.html
@@ -71,6 +71,11 @@ def loop(lmpptr,N,cut0):
 </PRE>
 <P><B>Description:</B>
 </P>
+<P>IMPORTANT NOTE: It is not currently possible to use the
+<A HREF = "python.html">python</A> command described in this section with Python 3,
+only with Python 2.  The C API changed from Python 2 to 3 and the
+LAMMPS code is not compatible with both.
+</P>
 <P>Define a Python function or execute a previously defined function.
 Arguments, including LAMMPS variables, can be passed to the function
 from the LAMMPS input script and a value returned by the Python
diff --git a/doc/python.txt b/doc/python.txt
index 6843f4e428..334478b41c 100644
--- a/doc/python.txt
+++ b/doc/python.txt
@@ -65,6 +65,11 @@ def loop(lmpptr,N,cut0):
 
 [Description:]
 
+IMPORTANT NOTE: It is not currently possible to use the
+"python"_python.html command described in this section with Python 3,
+only with Python 2.  The C API changed from Python 2 to 3 and the
+LAMMPS code is not compatible with both.
+
 Define a Python function or execute a previously defined function.
 Arguments, including LAMMPS variables, can be passed to the function
 from the LAMMPS input script and a value returned by the Python