introduce actual default/nullary constructor in cython wrapper

cyt/raw_eater.pxd

@@ -6,14 +6,22 @@ from libcpp.string cimport string
 from libcpp.vector cimport vector
 from libcpp cimport bool
 
-#cdef extern from "raweat.hpp":
+# to include implemenation/definition file
+#cdef extern from "raweat.cpp":
 #    pass
 
 # these method names have to match the C definitions of the methods!!
+#
+# for how to overload the constructor see
+# https://cython.readthedocs.io/en/latest/src/userguide/wrapping_CPlusPlus.html
 
 cdef extern from "../lib/raweat.hpp":
     cdef cppclass raw_eater:
+        # constructor(s)
+        raw_eater() except+
         raw_eater(string) except +
+        # set new file for decoding
+        void set_file(string)
         # get validity of data format
         bool get_valid()
         # get channel name and unit

cyt/raw_eater.pyx

@@ -2,38 +2,54 @@
 from raw_eater cimport raweater
 import numpy as np
 import re
+import os
 
 cdef class raweater:
 
-    # pointer to C++ instance (since there's no nullary constructor)
-    cdef raw_eater *rawit
+  # C++ instance of class => stack allocated (requires nullary constructor!)
+  cdef raw_eater rawit
 
-    def __cinit__(self, string rawfile):
-        self.rawit = new raw_eater(rawfile)
+  # pointer to C++ instance (if there's no nullary constructor)
+  # cdef raw_eater *rawit
 
-    def __dealloc__(self):
-        del self.rawit
+  def __cinit__(self, string rawfile = b''):
+    if rawfile.decode() == "":
+      self.rawit = raw_eater()
+      # self.rawit = new raw_eater()
+    else:
+      if not os.path.isfile(rawfile) :
+        raise ValueError("'" + str(rawfile) + "' does not exist")
+      self.rawit = raw_eater(rawfile)
+      # self.rawit = new raw_eater(rawfile)
 
-    def validity(self):
-        return self.rawit.get_valid()
+  # def __dealloc__(self):
+  #   del self.rawit
 
-    def channel_name(self):
-        return self.rawit.get_name()
+  def set_file(self, string rawfile):
+    if not os.path.isfile(rawfile) :
+      raise ValueError("'" + str(rawfile) + "' does not exist")
+    self.rawit.set_file(rawfile)
 
-    def unit(self):
-        return self.rawit.get_unit()
+  def validity(self):
+    return self.rawit.get_valid()
 
-    def dt(self):
-        return self.rawit.get_dt()
+  def channel_name(self):
+    return self.rawit.get_name()
 
-    def time_unit(self):
-        return self.rawit.get_temp_unit()
+  def unit(self):
+    return self.rawit.get_unit()
 
-    def get_time(self):
-        return self.rawit.get_time()
+  def dt(self):
+    return self.rawit.get_dt()
 
-    def get_channel(self):
-        return self.rawit.get_data()
+  def time_unit(self):
+    return self.rawit.get_temp_unit()
 
-    def write_table(self, const char* csvfile, char delimiter):
-        return self.rawit.write_table(csvfile,delimiter)
+  def get_time(self):
+    return self.rawit.get_time()
+
+  def get_channel(self):
+    return self.rawit.get_data()
+
+  def write_table(self, const char* csvfile, char delimiter):
+    self.rawit.write_table(csvfile,delimiter)