add python module interface to lammps_last_thermo, small consistency fixes

python/lammps/core.py

@@ -272,6 +272,9 @@ class lammps(object):
     self.lib.lammps_get_thermo.argtypes = [c_void_p, c_char_p]
     self.lib.lammps_get_thermo.restype = c_double
 
+    self.lib.lammps_last_thermo.argtypes = [c_void_p, c_char_p, c_int]
+    self.lib.lammps_last_thermo.restype = c_void_p
+
     self.lib.lammps_encode_image_flags.restype = self.c_imageint
 
     self.lib.lammps_config_has_package.argtypes = [c_char_p]
@@ -744,6 +747,57 @@ class lammps(object):
 
   # -------------------------------------------------------------------------
 
+  def last_thermo(self):
+    """Get a dictionary of the last thermodynamic output
+
+    This is a wrapper around the :cpp:func:`lammps_last_thermo`
+    function of the C-library interface.  It collects the cached thermo
+    data from the last timestep into a dictionary.  The return value
+    is None, if there has not been any thermo output yet.
+
+    :return: value of thermo keyword
+    :rtype: dict or None
+    """
+
+    rv = dict()
+    with ExceptionCheck(self):
+      ptr = self.lib.lammps_last_thermo(self.lmp, c_char_p("step".encode()), 0)
+    mystep = cast(ptr, POINTER(self.c_bigint)).contents.value
+    if mystep < 0:
+      return None
+
+    with ExceptionCheck(self):
+      ptr = self.lib.lammps_last_thermo(self.lmp, c_char_p("num".encode()), 0)
+    nfield = cast(ptr, POINTER(c_int)).contents.value
+
+    for i in range(nfield):
+      with ExceptionCheck(self):
+        ptr = self.lib.lammps_last_thermo(self.lmp, c_char_p("keyword".encode()), i)
+      kw = cast(ptr, c_char_p).value.decode()
+
+      # temporarily switch return type since this stores an int in a pointer
+      self.lib.lammps_last_thermo.restype = c_int
+      with ExceptionCheck(self):
+        typ = self.lib.lammps_last_thermo(self.lmp, c_char_p("type".encode()), i)
+      self.lib.lammps_last_thermo.restype = c_void_p
+      with ExceptionCheck(self):
+        ptr = self.lib.lammps_last_thermo(self.lmp, c_char_p("data".encode()), i)
+
+      if typ == LAMMPS_DOUBLE:
+        val = cast(ptr, POINTER(c_double)).contents.value
+      elif typ == LAMMPS_INT:
+        val = cast(ptr, POINTER(c_int)).contents.value
+      elif typ == LAMMPS_INT64:
+        val = cast(ptr, POINTER(c_int64)).contents.value
+      else:
+        # we should not get here
+        raise TypeError("Unknown LAMMPS data type " + str(typ))
+      rv[kw] = val
+
+    return rv
+
+  # -------------------------------------------------------------------------
+
   def extract_setting(self, name):
     """Query LAMMPS about global settings that can be expressed as an integer.
 

src/library.cpp

@@ -783,15 +783,15 @@ argument string.
      - no
    * - keyword
      - column keyword for thermo output
-     - const char pointer
+     - pointer to 0-terminated const char array
      - yes
    * - type
      - data type of thermo output column; see :cpp:enum:`_LMP_DATATYPE_CONST`
-     - const int
+     - const int (**not** a pointer)
      - yes
    * - data
      - actual field data for column
-     - pointer to either int, int64_t or double
+     - pointer to int, int64_t or double
      - yes
 
 \endverbatim

src/library.h

@@ -148,7 +148,7 @@ void lammps_commands_string(void *handle, const char *str);
 
 double lammps_get_natoms(void *handle);
 double lammps_get_thermo(void *handle, const char *keyword);
-void *lammps_last_thermo(void *handle, const char *what, int idx);
+void *lammps_last_thermo(void *handle, const char *what, int index);
 
 void lammps_extract_box(void *handle, double *boxlo, double *boxhi, double *xy, double *yz,
                         double *xz, int *pflags, int *boxflag);