diff --git a/nac3core/src/codegen/expr.rs b/nac3core/src/codegen/expr.rs
index 013785e5f..4d290e27c 100644
--- a/nac3core/src/codegen/expr.rs
+++ b/nac3core/src/codegen/expr.rs
@@ -114,10 +114,28 @@ impl<'ctx, 'a> CodeGenContext<'ctx, 'a> {
         let symbol = {
             // make sure this lock guard is dropped at the end of this scope...
             let def = definition.read();
-            if let TopLevelDef::Function { instance_to_symbol, .. } = &*def {
-                instance_to_symbol.get(&key).cloned()
-            } else {
-                unreachable!()
+            match &*def {
+                TopLevelDef::Function { instance_to_symbol, .. } => {
+                    instance_to_symbol.get(&key).cloned()
+                }
+                TopLevelDef::Class { methods, .. } => {
+                    // TODO: what about other fields that require alloca?
+                    let mut fun_id = None;
+                    for (name, _, id) in methods.iter() {
+                        if name == "__init__" {
+                            fun_id = Some(*id);
+                        }
+                    }
+                    let fun_id = fun_id.unwrap();
+
+                    let ty = self.get_llvm_type(fun.0.ret).into_pointer_type();
+                    let zelf_ty: BasicTypeEnum = ty.get_element_type().try_into().unwrap();
+                    let zelf = self.builder.build_alloca(zelf_ty, "alloca").into();
+                    let mut sign = fun.0.clone();
+                    sign.ret = self.primitives.none;
+                    self.gen_call(Some((fun.0.ret, zelf)), (&sign, fun_id), params);
+                    return Some(zelf);
+                }
             }
         }
         .unwrap_or_else(|| {
@@ -164,7 +182,7 @@ impl<'ctx, 'a> CodeGenContext<'ctx, 'a> {
                         })
                         .collect();
 
-                    let signature = FunSignature {
+                    let mut signature = FunSignature {
                         args: fun
                             .0
                             .args
@@ -186,6 +204,13 @@ impl<'ctx, 'a> CodeGenContext<'ctx, 'a> {
                             .collect(),
                     };
 
+                    if let Some(obj) = &obj {
+                        signature.args.insert(
+                            0,
+                            FuncArg { name: "self".into(), ty: obj.0, default_value: None },
+                        );
+                    }
+
                     let unifier = (unifier.get_shared_unifier(), *primitives);
 
                     task = Some(CodeGenTask {
@@ -209,7 +234,11 @@ impl<'ctx, 'a> CodeGenContext<'ctx, 'a> {
         }
 
         let fun_val = self.module.get_function(&symbol).unwrap_or_else(|| {
-            let params = fun.0.args.iter().map(|arg| self.get_llvm_type(arg.ty)).collect_vec();
+            let mut args = fun.0.args.clone();
+            if let Some(obj) = &obj {
+                args.insert(0, FuncArg { name: "self".into(), ty: obj.0, default_value: None });
+            }
+            let params = args.iter().map(|arg| self.get_llvm_type(arg.ty)).collect_vec();
             let fun_ty = if self.unifier.unioned(fun.0.ret, self.primitives.none) {
                 self.ctx.void_type().fn_type(&params, false)
             } else {
@@ -227,7 +256,11 @@ impl<'ctx, 'a> CodeGenContext<'ctx, 'a> {
             mapping.insert(k.name, self.gen_symbol_val(&k.default_value.unwrap()));
         }
         // reorder the parameters
-        let params = fun.0.args.iter().map(|arg| mapping.remove(&arg.name).unwrap()).collect_vec();
+        let mut params =
+            fun.0.args.iter().map(|arg| mapping.remove(&arg.name).unwrap()).collect_vec();
+        if let Some(obj) = obj {
+            params.insert(0, obj.1);
+        }
         self.builder.build_call(fun_val, &params, "call").try_as_basic_value().left()
     }
 
@@ -607,26 +640,53 @@ impl<'ctx, 'a> CodeGenContext<'ctx, 'a> {
                 phi.as_basic_value()
             }
             ExprKind::Call { func, args, keywords } => {
-                if let ExprKind::Name { id, .. } = &func.as_ref().node {
-                    // TODO: handle primitive casts and function pointers
-                    let fun = self.resolver.get_identifier_def(&id).expect("Unknown identifier");
-                    let mut params =
-                        args.iter().map(|arg| (None, self.gen_expr(arg).unwrap())).collect_vec();
-                    let kw_iter = keywords.iter().map(|kw| {
-                        (
-                            Some(kw.node.arg.as_ref().unwrap().clone()),
-                            self.gen_expr(&kw.node.value).unwrap(),
-                        )
-                    });
-                    params.extend(kw_iter);
-                    let signature = self
-                        .unifier
-                        .get_call_signature(*self.calls.get(&expr.location.into()).unwrap())
-                        .unwrap();
-                    return self.gen_call(None, (&signature, fun), params);
-                } else {
-                    // TODO: method
-                    unimplemented!()
+                let mut params =
+                    args.iter().map(|arg| (None, self.gen_expr(arg).unwrap())).collect_vec();
+                let kw_iter = keywords.iter().map(|kw| {
+                    (
+                        Some(kw.node.arg.as_ref().unwrap().clone()),
+                        self.gen_expr(&kw.node.value).unwrap(),
+                    )
+                });
+                params.extend(kw_iter);
+                let signature = self
+                    .unifier
+                    .get_call_signature(*self.calls.get(&expr.location.into()).unwrap())
+                    .unwrap();
+                match &func.as_ref().node {
+                    ExprKind::Name { id, .. } => {
+                        // TODO: handle primitive casts and function pointers
+                        let fun =
+                            self.resolver.get_identifier_def(&id).expect("Unknown identifier");
+                        return self.gen_call(None, (&signature, fun), params);
+                    }
+                    ExprKind::Attribute { value, attr, .. } => {
+                        let val = self.gen_expr(value).unwrap();
+                        let id = if let TypeEnum::TObj { obj_id, .. } =
+                            &*self.unifier.get_ty(value.custom.unwrap())
+                        {
+                            *obj_id
+                        } else {
+                            unreachable!()
+                        };
+                        let fun_id = {
+                            let defs = self.top_level.definitions.read();
+                            let obj_def = defs.get(id.0).unwrap().read();
+                            if let TopLevelDef::Class { methods, .. } = &*obj_def {
+                                let mut fun_id = None;
+                                for (name, _, id) in methods.iter() {
+                                    if name == attr {
+                                        fun_id = Some(*id);
+                                    }
+                                }
+                                fun_id.unwrap()
+                            } else {
+                                unreachable!()
+                            }
+                        };
+                        return self.gen_call(Some((value.custom.unwrap(), val)), (&signature, fun_id), params);
+                    }
+                    _ => unimplemented!(),
                 }
             }
             ExprKind::Subscript { value, slice, .. } => {
diff --git a/nac3core/src/codegen/mod.rs b/nac3core/src/codegen/mod.rs
index 1c3e4e16d..413572906 100644
--- a/nac3core/src/codegen/mod.rs
+++ b/nac3core/src/codegen/mod.rs
@@ -341,8 +341,16 @@ pub fn gen_func<'ctx>(
         unifier,
     };
 
+    let mut returned = false;
     for stmt in task.body.iter() {
-        code_gen_context.gen_stmt(stmt);
+        returned = code_gen_context.gen_stmt(stmt);
+        if returned {
+            break;
+        }
+    }
+    // after static analysis, only void functions can have no return at the end.
+    if !returned {
+        code_gen_context.builder.build_return(None);
     }
 
     let CodeGenContext { builder, module, .. } = code_gen_context;
diff --git a/nac3core/src/toplevel/composer.rs b/nac3core/src/toplevel/composer.rs
index 15523d1d9..d1099a642 100644
--- a/nac3core/src/toplevel/composer.rs
+++ b/nac3core/src/toplevel/composer.rs
@@ -34,16 +34,18 @@ impl Default for TopLevelComposer {
 impl TopLevelComposer {
     /// return a composer and things to make a "primitive" symbol resolver, so that the symbol
     /// resolver can later figure out primitive type definitions when passed a primitive type name
-    pub fn new(builtins: Vec<(String, FunSignature)>) -> (Self, HashMap<String, DefinitionId>, HashMap<String, Type>) {
+    pub fn new(
+        builtins: Vec<(String, FunSignature)>,
+    ) -> (Self, HashMap<String, DefinitionId>, HashMap<String, Type>) {
         let primitives = Self::make_primitives();
 
         let mut definition_ast_list = {
             let top_level_def_list = vec![
-                Arc::new(RwLock::new(Self::make_top_level_class_def(0, None, "int32"))),
-                Arc::new(RwLock::new(Self::make_top_level_class_def(1, None, "int64"))),
-                Arc::new(RwLock::new(Self::make_top_level_class_def(2, None, "float"))),
-                Arc::new(RwLock::new(Self::make_top_level_class_def(3, None, "bool"))),
-                Arc::new(RwLock::new(Self::make_top_level_class_def(4, None, "none"))),
+                Arc::new(RwLock::new(Self::make_top_level_class_def(0, None, "int32", None))),
+                Arc::new(RwLock::new(Self::make_top_level_class_def(1, None, "int64", None))),
+                Arc::new(RwLock::new(Self::make_top_level_class_def(2, None, "float", None))),
+                Arc::new(RwLock::new(Self::make_top_level_class_def(3, None, "bool", None))),
+                Arc::new(RwLock::new(Self::make_top_level_class_def(4, None, "none", None))),
             ];
             let ast_list: Vec<Option<ast::Stmt<()>>> = vec![None, None, None, None, None];
             izip!(top_level_def_list, ast_list).collect_vec()
@@ -69,10 +71,10 @@ impl TopLevelComposer {
         let mut defined_class_name: HashSet<String> = Default::default();
         let mut defined_function_name: HashSet<String> = Default::default();
         let method_class: HashMap<DefinitionId, DefinitionId> = Default::default();
-        
+
         let mut built_in_id: HashMap<String, DefinitionId> = Default::default();
         let mut built_in_ty: HashMap<String, Type> = Default::default();
-        
+
         for (name, sig) in builtins {
             let fun_sig = unifier.add_ty(TypeEnum::TFunc(RefCell::new(sig)));
             built_in_ty.insert(name.clone(), fun_sig);
@@ -80,22 +82,20 @@ impl TopLevelComposer {
             definition_ast_list.push((
                 Arc::new(RwLock::new(TopLevelDef::Function {
                     name: name.clone(),
+                    simple_name: name.clone(),
                     signature: fun_sig,
                     instance_to_stmt: HashMap::new(),
-                    instance_to_symbol: [("".to_string(), name.clone())]
-                        .iter()
-                        .cloned()
-                        .collect(),
+                    instance_to_symbol: [("".to_string(), name.clone())].iter().cloned().collect(),
                     var_id: Default::default(),
                     resolver: None,
                 })),
-                None
+                None,
             ));
             defined_class_method_name.insert(name.clone());
             defined_class_name.insert(name.clone());
             defined_function_name.insert(name);
         }
-        
+
         (
             TopLevelComposer {
                 built_in_num: definition_ast_list.len(),
@@ -160,11 +160,13 @@ impl TopLevelComposer {
 
                 // since later when registering class method, ast will still be used,
                 // here push None temporarly, later will move the ast inside
+                let constructor_ty = self.unifier.get_fresh_var().0;
                 let mut class_def_ast = (
                     Arc::new(RwLock::new(Self::make_top_level_class_def(
                         class_def_id,
                         resolver.clone(),
                         name,
+                        Some(constructor_ty)
                     ))),
                     None,
                 );
@@ -215,6 +217,7 @@ impl TopLevelComposer {
                             method_name.clone(),
                             RwLock::new(Self::make_top_level_function_def(
                                 global_class_method_name,
+                                method_name.clone(),
                                 // later unify with parsed type
                                 dummy_method_type.0,
                                 resolver.clone(),
@@ -251,14 +254,7 @@ impl TopLevelComposer {
                     self.definition_ast_list.push((def, Some(ast)));
                 }
 
-                // put the constructor into the def_list
-                self.definition_ast_list.push((
-                    RwLock::new(TopLevelDef::Initializer { class_id: DefinitionId(class_def_id) })
-                        .into(),
-                    None,
-                ));
-
-                Ok((class_name, DefinitionId(class_def_id), None))
+                Ok((class_name, DefinitionId(class_def_id), Some(constructor_ty)))
             }
 
             ast::StmtKind::FunctionDef { name, .. } => {
@@ -278,6 +274,8 @@ impl TopLevelComposer {
                 // add to the definition list
                 self.definition_ast_list.push((
                     RwLock::new(Self::make_top_level_function_def(
+                        // TODO: is this fun_name or the above name with mod_path?
+                        name.into(),
                         name.into(),
                         // dummy here, unify with correct type later
                         ty_to_be_unified,
@@ -801,7 +799,7 @@ impl TopLevelComposer {
             resolver,
             type_vars,
             ..
-        } = class_def.deref_mut()
+        } = &mut *class_def
         {
             if let ast::StmtKind::ClassDef { name, bases, body, .. } = &class_ast {
                 (
@@ -1161,32 +1159,36 @@ impl TopLevelComposer {
 
     /// step 5, analyze and call type inferecer to fill the `instance_to_stmt` of topleveldef::function
     fn analyze_function_instance(&mut self) -> Result<(), String> {
-        for (id, (def, ast)) in self.definition_ast_list.iter().enumerate().skip(self.built_in_num) {
+        for (id, (def, ast)) in self.definition_ast_list.iter().enumerate().skip(self.built_in_num)
+        {
             let mut function_def = def.write();
-            if let TopLevelDef::Function {
-                instance_to_stmt,
-                name,
-                signature,
-                var_id,
-                resolver,
-                ..
-            } = &mut *function_def
+            if let TopLevelDef::Function { instance_to_stmt, name, simple_name, signature, resolver, .. } =
+                &mut *function_def
             {
-                if let TypeEnum::TFunc(func_sig) = self.unifier.get_ty(*signature).as_ref() {
+               if let TypeEnum::TFunc(func_sig) = self.unifier.get_ty(*signature).as_ref() {
                     let FunSignature { args, ret, vars } = &*func_sig.borrow();
                     // None if is not class method
                     let self_type = {
                         if let Some(class_id) = self.method_class.get(&DefinitionId(id)) {
                             let class_def = self.definition_ast_list.get(class_id.0).unwrap();
                             let class_def = class_def.0.read();
-                            if let TopLevelDef::Class { type_vars, .. } = &*class_def {
+                            if let TopLevelDef::Class { type_vars, constructor, .. } = &*class_def {
                                 let ty_ann = make_self_type_annotation(type_vars, *class_id);
-                                Some(get_type_from_type_annotation_kinds(
+                                let self_ty = get_type_from_type_annotation_kinds(
                                     self.extract_def_list().as_slice(),
                                     &mut self.unifier,
                                     &self.primitives_ty,
                                     &ty_ann,
-                                )?)
+                                )?;
+                                if simple_name == "__init__" {
+                                    let fn_type = self.unifier.add_ty(TypeEnum::TFunc(RefCell::new(FunSignature {
+                                        args: args.clone(),
+                                        ret: self_ty,
+                                        vars: vars.clone()
+                                    })));
+                                    self.unifier.unify(fn_type, constructor.unwrap())?;
+                                }
+                                Some(self_ty)
                             } else {
                                 unreachable!("must be class def")
                             }
@@ -1227,8 +1229,7 @@ impl TopLevelComposer {
                         let inst_ret = self.unifier.subst(*ret, &subst).unwrap_or(*ret);
                         let inst_args = {
                             let unifier = &mut self.unifier;
-                            args
-                                .iter()
+                            args.iter()
                                 .map(|a| FuncArg {
                                     name: a.name.clone(),
                                     ty: unifier.subst(a.ty, &subst).unwrap_or(a.ty),
@@ -1319,15 +1320,15 @@ impl TopLevelComposer {
                                     .sorted()
                                     .map(|id| {
                                         let ty = subst.get(id).unwrap();
-                                        unifier.stringify(*ty, &mut |id| id.to_string(), &mut |id| id.to_string())
-                                    }).join(", ")
-                            },
-                            FunInstance {
-                                body: fun_body,
-                                unifier_id: 0,
-                                calls,
-                                subst,
+                                        unifier.stringify(
+                                            *ty,
+                                            &mut |id| id.to_string(),
+                                            &mut |id| id.to_string(),
+                                        )
+                                    })
+                                    .join(", ")
                             },
+                            FunInstance { body: fun_body, unifier_id: 0, calls, subst },
                         );
                     }
                 } else {
diff --git a/nac3core/src/toplevel/helper.rs b/nac3core/src/toplevel/helper.rs
index dd70fa908..f128b2757 100644
--- a/nac3core/src/toplevel/helper.rs
+++ b/nac3core/src/toplevel/helper.rs
@@ -50,7 +50,6 @@ impl TopLevelDef {
                     r
                 }
             ),
-            TopLevelDef::Initializer { class_id } => format!("Initializer {{ {:?} }}", class_id),
         }
     }
 }
@@ -94,6 +93,7 @@ impl TopLevelComposer {
         index: usize,
         resolver: Option<Arc<Box<dyn SymbolResolver + Send + Sync>>>,
         name: &str,
+        constructor: Option<Type>
     ) -> TopLevelDef {
         TopLevelDef::Class {
             name: name.to_string(),
@@ -102,6 +102,7 @@ impl TopLevelComposer {
             fields: Default::default(),
             methods: Default::default(),
             ancestors: Default::default(),
+            constructor,
             resolver,
         }
     }
@@ -109,11 +110,13 @@ impl TopLevelComposer {
     /// when first registering, the type is a invalid value
     pub fn make_top_level_function_def(
         name: String,
+        simple_name: String,
         ty: Type,
         resolver: Option<Arc<Box<dyn SymbolResolver + Send + Sync>>>,
     ) -> TopLevelDef {
         TopLevelDef::Function {
             name,
+            simple_name,
             signature: ty,
             var_id: Default::default(),
             instance_to_symbol: Default::default(),
diff --git a/nac3core/src/toplevel/mod.rs b/nac3core/src/toplevel/mod.rs
index 206aefe9c..4076931fe 100644
--- a/nac3core/src/toplevel/mod.rs
+++ b/nac3core/src/toplevel/mod.rs
@@ -53,10 +53,14 @@ pub enum TopLevelDef {
         ancestors: Vec<TypeAnnotation>,
         // symbol resolver of the module defined the class, none if it is built-in type
         resolver: Option<Arc<Box<dyn SymbolResolver + Send + Sync>>>,
+        // constructor type
+        constructor: Option<Type>,
     },
     Function {
         // prefix for symbol, should be unique globally, and not ending with numbers
         name: String,
+        // simple name, the same as in method/function definition
+        simple_name: String,
         // function signature.
         signature: Type,
         // instantiated type variable IDs
@@ -75,9 +79,6 @@ pub enum TopLevelDef {
         // symbol resolver of the module defined the class
         resolver: Option<Arc<Box<dyn SymbolResolver + Send + Sync>>>,
     },
-    Initializer {
-        class_id: DefinitionId,
-    },
 }
 
 pub struct TopLevelContext {
diff --git a/nac3standalone/mandelbrot.py b/nac3standalone/mandelbrot.py
index 7afd28a7c..07d0bcbf6 100644
--- a/nac3standalone/mandelbrot.py
+++ b/nac3standalone/mandelbrot.py
@@ -1,64 +1,20 @@
-def y_scale(maxX: float, minX: float, height: float, width: float, aspectRatio: float) -> float:
-    return (maxX-minX)*(height/width)*aspectRatio
+class A:
+    a: int32
+    def __init__(self, a: int32):
+        self.a = a
 
-def check_smaller_than_sixteen(i: int32) -> bool:
-    return i < 16
+    def get_a(self) -> int32:
+        return self.a
 
-def rec(x: int32):
-    if x > 1:
-        output(x)
-        rec(x - 1)
-        return
-    else:
-        output(-1)
-        return
-
-def fib(n: int32) -> int32:
-    if n <= 2:
-        return 1
-    else:
-        return fib(n - 1) + fib(n - 2)
-
-def draw():
-    minX = -2.0
-    maxX = 1.0
-    width = 78.0
-    height = 36.0
-    aspectRatio = 2.0
-
-    # test = 1.0 + 1
-
-    yScale = y_scale(maxX, minX, height, width, aspectRatio)
-
-    y = 0.0
-    while y < height:
-        x = 0.0
-        while x < width:
-            c_r = minX+x*(maxX-minX)/width
-            c_i = y*yScale/height-yScale/2.0
-            z_r = c_r
-            z_i = c_i
-            i = 0
-            while check_smaller_than_sixteen(i):
-                if z_r*z_r + z_i*z_i > 4.0:
-                    break
-                new_z_r = (z_r*z_r)-(z_i*z_i) + c_r
-                z_i = 2.0*z_r*z_i + c_i
-                z_r = new_z_r
-                i = i + 1
-            output(i)
-            x = x + 1.0
-        output(-1)
-        y = y + 1.0
-    
-    return
+    def get_self(self) -> A:
+        return self
 
 def run() -> int32:
-    rec(5)
+    a = A(10)
+    output(a.a)
 
-    output(fib(10))
-    output(-1)
-    
-    draw()
+    a = A(20)
+    output(a.a)
+    output(a.get_a())
     return 0
 
diff --git a/nac3standalone/src/main.rs b/nac3standalone/src/main.rs
index 07b994157..acbfb00d8 100644
--- a/nac3standalone/src/main.rs
+++ b/nac3standalone/src/main.rs
@@ -1,14 +1,11 @@
-use std::time::SystemTime;
-use std::{collections::HashSet, fs};
-
+use std::fs;
 use inkwell::{
     passes::{PassManager, PassManagerBuilder},
     targets::*,
     OptimizationLevel,
 };
 use nac3core::typecheck::type_inferencer::PrimitiveStore;
-use parking_lot::RwLock;
-use rustpython_parser::parser;
+use rustpython_parser::{parser, ast::StmtKind};
 use std::{collections::HashMap, path::Path, sync::Arc};
 
 use nac3core::{
@@ -55,11 +52,17 @@ fn main() {
     );
 
     for stmt in parser::parse_program(&program).unwrap().into_iter() {
+        let is_class = matches!(stmt.node, StmtKind::ClassDef{ .. });
         let (name, def_id, ty) = composer.register_top_level(
             stmt,
             Some(resolver.clone()),
             "__main__".into(),
         ).unwrap();
+
+        if is_class {
+            internal_resolver.add_id_type(name.clone(), ty.unwrap());
+        }
+
         internal_resolver.add_id_def(name.clone(), def_id);
         if let Some(ty) = ty {
             internal_resolver.add_id_type(name, ty);