Call class in main python

Python how to use class in main c

So after taking that into account it should look like this: Solution 2: To understand why what you wrote failed, you need to know a little bit about how class definitions work in Python. As you may know, Python is an interpreted language: there is a program which reads through Python files and executes them as it goes.

Define Python class from C

Yes, you can create your own class types in C. From the C API a Python type/class is an instance of the PyTypeObject structure filled in appropriately for your type. The whole procedure for doing this is outlined nicely in the following tutorial:

This will walk you through defining the initial core type and then adding data and methods to the type/class. At first it may seem like an awful lot of work just to get a class implemented in C, but once you do it a few times and get comfortable with it, it’s really not so bad.

Here is a bare bones implementation of the Test class you define in your question.

#include #include "structmember.h" typedef struct < PyObject_HEAD /* Your internal 'loc' data. */ int loc; >Test; static void MyTest_dealloc(Test* self) < self->ob_type->tp_free((PyObject*)self); > static PyObject * Test_new(PyTypeObject *type, PyObject *args, PyObject *kwds) < Test *self; self = (Test *)type->tp_alloc(type, 0); self->loc = 0; return (PyObject *)self; > static int Test_init(Test *self, PyObject *args, PyObject *kwds) < if (! PyArg_ParseTuple(args, "i", &self->loc)) return -1; return 0; > static PyMemberDef Test_members[] = < , /* Sentinel */ >; static PyObject * Test_foo(Test* self, PyObject *args) < int data; PyObject *result; if (! PyArg_ParseTuple(args, "i", &data)) < return NULL; >/* We'll just return data + loc as our result. */ result = Py_BuildValue("i", data + self->loc); return result; > static PyMethodDef Test_methods[] = < , /* Sentinel */ >; static PyTypeObject mytest_MyTestType = < PyObject_HEAD_INIT(NULL) 0, /*ob_size*/ "mytest.MyTest", /*tp_name*/ sizeof(Test), /*tp_basicsize*/ 0, /*tp_itemsize*/ (destructor)MyTest_dealloc,/*tp_dealloc*/ 0, /*tp_print*/ 0, /*tp_getattr*/ 0, /*tp_setattr*/ 0, /*tp_compare*/ 0, /*tp_repr*/ 0, /*tp_as_number*/ 0, /*tp_as_sequence*/ 0, /*tp_as_mapping*/ 0, /*tp_hash */ 0, /*tp_call*/ 0, /*tp_str*/ 0, /*tp_getattro*/ 0, /*tp_setattro*/ 0, /*tp_as_buffer*/ Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,/*tp_flags*/ "MyTest objects", /* tp_doc */ 0, /* tp_traverse */ 0, /* tp_clear */ 0, /* tp_richcompare */ 0, /* tp_weaklistoffset */ 0, /* tp_iter */ 0, /* tp_iternext */ Test_methods, /* tp_methods */ Test_members, /* tp_members */ 0, /* tp_getset */ 0, /* tp_base */ 0, /* tp_dict */ 0, /* tp_descr_get */ 0, /* tp_descr_set */ 0, /* tp_dictoffset */ (initproc)Test_init,/* tp_init */ 0, /* tp_alloc */ Test_new, /* tp_new */ >; static PyMethodDef mytest_methods[] = < /* Sentinel */ >; #ifndef PyMODINIT_FUNC /* declarations for DLL import/export */ #define PyMODINIT_FUNC void #endif PyMODINIT_FUNC initmytest(void)

And its usage from the Python interpreter:

>>> from mytest import Test >>> t = Test(5) >>> t.foo(10) 15 

May be it’s not your question ans. But it can be helpful.

#include "boost/python.hpp" using namespace boost::python; int main()

Python Classes/Objects, class definitions cannot be empty, but if you for some reason have a class definition with no content, put in the pass statement to avoid getting an error.

How can I use C++ class in Python?

Look into Boost.Python. It’s a library to write python modules with C++.

Also look into SWIG which can also handle modules for other scripting languages. I’ve used it in the past to write modules for my class and use them within python. Works great.

You can do it manually by using the Python/C API, writing the interface yourself. It’s pretty lowlevel, but you will gain a lot of additional knowledge of how Python works behind the scene (And you will need it when you use SWIG anyway).

ctypes is good. It is really easy to use, and it comes standard with Python. Unfortunately it can only talk to shared libraries (Unix) or DLLs (Windows) that have a C-style interface, which means you can’t directly interface to a C++ object. But you could use a handle system where a handle refers to a particular object.

I think that is simple, easy to understand, and doesn’t require extra libraries.

I would suggest you try SWIG or sip (KDE/PyQt).

SWIG link : http://www.swig.org/
SIP link: http://freshmeat.net/projects/python-sip/

These can be used to wrap C++ classes and provide a Pythonic interface to them.

How can we write main as a class in C++?, How to successfully create a class named main? When the class name is main, it is compulsory to use keyword class or struct to declare objects.

Defining a Python class in both Python and C

Personally, I wouldn’t try and do object-oriented stuff in C. I’d stick to writing a module which exposes some (stateless) functions.

If I wanted the Python interface to be object oriented, I’d write a class in Python which imports that (C extension) module and consumes functions from it. Maintaining of any state would all be done in Python.

You could instead define a _Matrix type which you then extend with a traditional OOP approach

from mymodule._mymodule import _Matrix; class Matrix(_Matrix): def __str__(self): return "This is a matrix!" 

Classes vs. Functions, This is not exactly true. Classes also allow for dispatching on types. · Forcing your logic, you can include the class functions (for example as a vtable)

Main method in Python

def main(): dog = Animal() dog.set_owner('Sue') print dog.get_owner() dog.noise() if __name__ =='__main__':main() 

should not be in the class. When you take it outside (no indent) it should work.

So after taking that into account it should look like this:

class Animal: __hungry = "yes" __name = "no name" __owner = "no owner" def __init__(self): pass def set_owner(self,newOwner): self.__owner= newOwner return def get_owner(self): return self.__owner def set_name(self,newName): self.__name= newName return def get_name(self): return self.__name def noise(self): print('errr') return def __hiddenmethod(self): print("hard to find") def main(): dog = Animal() dog.set_owner('Sue') print dog.get_owner() dog.noise() if __name__ =='__main__': main() 

To understand why what you wrote failed, you need to know a little bit about how class definitions work in Python. As you may know, Python is an interpreted language: there is a program which reads through Python files and executes them as it goes. When the interpreter encounters a class definition, it does the following:

1. Creates a new namespace (record of all the variable names) in which the class variables and methods will be stored.
2. Extracts all the code within the class definition (as determined by its indentation) and runs that code. This will populate the namespace which it just created.
3. Creates a new class object whose namespace is that given above, and with base classes those given in the definition.
4. Binds the name of the class to this object.

So what happened when you indented the main function inside your code? While inside step 2, you referred to the name Animal . But this name isn’t defined until step 4! Indeed, it can’t be defined at the stage you referred to it, because that would be circular. When you move main outside of the class definition, it won’t be executed until after steps 1-4 have been completed, and hence the name Animal will already be bound.

By the way, the code you have written is not good Python. You should probably try to find a better tutorial; the usual recommendation is «Dive Into Python». I’ve rewritten it as it should be done:

 class Animal(object): def __init__(self, hungry="yes", name=None, owner=None): self.hungry = hungry self.name = name self.owner = owner def noise(self): print('errr') def _internal_method(self): print("hard to find") if __name__ =='__main__': dog = Animal() dog.owner = 'Sue' print dog.owner dog.noise() 

The following construct is worth having in most of your code — particularly if you are running in multiple environments.

if __name__ =='__main__': main() 

Access Modifiers in C++, Now we can correlate these core members to data members or member functions of a class, which in turn can be correlated to the R&A Wing. These

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Python main call within class

I haven’t done much python — coming from a C/java background — so excuse me for asking such a simple question. I am using Pydev in Eclipse to write this simple program, and all I want it to do is to execute my main function:

class Example(): if __name__ == '__main__': Example().main()  

class Example(object): def run(self): print "Hello, world!" if __name__ == '__main__': Example().run() 

def main(): print "Hello, world!" if __name__ == '__main__': main() 

if __name__ == '__main__': print "Hello, world!" 

class Example(object): def main(self): print "Hello World!" if __name__ == '__main__': Example().main() 

class foo(): def print_hello(self): print("Hello") # This next line will produce an ERROR! self.print_hello() #  

class RandomPrograms: def __init__(self): pass def func1(self): new_dic=<> dlist=[] for x in range(0,3): new_dic["data<>".format(x)]=x dlist.append(new_dic.copy()) print (dlist) def main(self): abc=RandomPrograms() abc.func1() if __name__ == "__main__": RandomPrograms.main() 

class RandomPrograms: def __init__(self): pass def func1(self): new_dic=<> dlist=[] for x in range(0,3): new_dic["data<>".format(x)]=x dlist.append(new_dic.copy()) print (dlist) @staticmethod def main(): abc=RandomPrograms() abc.func1() if __name__ == "__main__": RandomPrograms.main() 

class RandomPrograms: def __init__(self): self.func1() def func1(self): new_dic=<> dlist=[] for x in range(3): new_dic[f"data"]=x dlist.append(new_dic) print(dlist) if __name__ == "__main__": RandomPrograms() 

class A(): def __init__(self): pass def start_the_process(self): self.b = B() self.b.add_values(2, 3) def print_result(self, result): print(result) class B(): def __init__(self): pass def add_values(self, val1, val2): a.print_result(val1 + val2) def main(): global a a = A() a.start_the_process() if __name__ == '__main__': main() 

class A(): def __init__(self): pass def start_the_process(self): self.b = B(self) self.b.add_values(2, 3) def print_result(self, result): print(result) class B(): def __init__(self, a): self.a = a def add_values(self, val1, val2): self.a.print_result(val1 + val2) def main(): a = A() a.start_the_process() if __name__ == '__main__': main()