diff --git a/src/builtins.h b/src/builtins.h
index 59db54ad..b653ea25 100644
--- a/src/builtins.h
+++ b/src/builtins.h
@@ -270,28 +270,11 @@ class dict:
             a.append(k.__json__()+': '+v.__json__())
         return '{'+ ', '.join(a) + '}'
 
-import json as _json
+import ffi
 
-def jsonrpc(method, params, raw=False):
-  assert type(method) is str
-  assert type(params) is list or type(params) is tuple
-  data = {
-    'jsonrpc': '2.0',
-    'method': method,
-    'params': params,
-  }
-  ret = __string_channel_call(_json.dumps(data))
-  ret = _json.loads(ret)
-  if raw:
-    return ret
-  assert type(ret) is dict
-  if 'result' in ret:
-    return ret['result']
-  raise JsonRpcError(ret['error']['message'])
+def input():
+  return ffi.input()
 
-def input(prompt=None):
-  return jsonrpc('input', [prompt])
-  
 class FileIO:
   def __init__(self, path, mode):
     assert type(path) is str
@@ -299,19 +282,19 @@ class FileIO:
     assert mode in ['r', 'w', 'rt', 'wt']
     self.path = path
     self.mode = mode
-    self.fp = jsonrpc('fopen', [path, mode])
+    self.fp = ffi.fopen(path, mode)
 
   def read(self):
     assert self.mode in ['r', 'rt']
-    return jsonrpc('fread', [self.fp])
+    return ffi.fread(self.fp)
 
   def write(self, s):
     assert self.mode in ['w', 'wt']
     assert type(s) is str
-    jsonrpc('fwrite', [self.fp, s])
+    ffi.fwrite(self.fp, s)
 
   def close(self):
-    jsonrpc('fclose', [self.fp])
+    ffi.fclose(self.fp)
 
   def __enter__(self):
     pass
@@ -423,42 +406,6 @@ class set:
         return self._a.keys().__iter__()
 )";
 
-const char* __OS_CODE = R"(
-def listdir(path):
-  assert type(path) is str
-  return jsonrpc("os.listdir", [path])
-
-def mkdir(path):
-  assert type(path) is str
-  return jsonrpc("os.mkdir", [path])
-
-def rmdir(path):
-  assert type(path) is str
-  return jsonrpc("os.rmdir", [path])
-
-def remove(path):
-  assert type(path) is str
-  return jsonrpc("os.remove", [path])
-
-path = object()
-
-def __path4exists(path):
-  assert type(path) is str
-  return jsonrpc("os.path.exists", [path])
-path.exists = __path4exists
-del __path4exists
-
-def __path4join(*paths):
-  s = '/'.join(paths)
-  s = s.replace('\\', '/')
-  s = s.replace('//', '/')
-  s = s.replace('//', '/')
-  return s
-
-path.join = __path4join
-del __path4join
-)";
-
 const char* __RANDOM_CODE = R"(
 import time as _time
 
diff --git a/src/pocketpy.h b/src/pocketpy.h
index e9275fe0..1d31936d 100644
--- a/src/pocketpy.h
+++ b/src/pocketpy.h
@@ -316,7 +316,7 @@ void __initializeBuiltinFunctions(VM* _vm) {
         }
 
         int _index = (int)vm->PyInt_AS_C(args[1]);
-        _index = vm->normalizedIndex(_index, _self.u8_length());
+        _index = vm->normalized_index(_index, _self.u8_length());
         return vm->PyStr(_self.u8_getitem(_index));
     });
 
@@ -434,14 +434,14 @@ void __initializeBuiltinFunctions(VM* _vm) {
         }
 
         int _index = (int)vm->PyInt_AS_C(args[1]);
-        _index = vm->normalizedIndex(_index, _self.size());
+        _index = vm->normalized_index(_index, _self.size());
         return _self[_index];
     });
 
     _vm->bindMethod<2>("list", "__setitem__", [](VM* vm, const pkpy::ArgList& args) {
         PyVarList& _self = vm->PyList_AS_C(args[0]);
         int _index = (int)vm->PyInt_AS_C(args[1]);
-        _index = vm->normalizedIndex(_index, _self.size());
+        _index = vm->normalized_index(_index, _self.size());
         _self[_index] = args[2];
         return vm->None;
     });
@@ -449,7 +449,7 @@ void __initializeBuiltinFunctions(VM* _vm) {
     _vm->bindMethod<1>("list", "__delitem__", [](VM* vm, const pkpy::ArgList& args) {
         PyVarList& _self = vm->PyList_AS_C(args[0]);
         int _index = (int)vm->PyInt_AS_C(args[1]);
-        _index = vm->normalizedIndex(_index, _self.size());
+        _index = vm->normalized_index(_index, _self.size());
         _self.erase(_self.begin() + _index);
         return vm->None;
     });
@@ -472,7 +472,7 @@ void __initializeBuiltinFunctions(VM* _vm) {
     _vm->bindMethod<1>("tuple", "__getitem__", [](VM* vm, const pkpy::ArgList& args) {
         const PyVarList& _self = vm->PyTuple_AS_C(args[0]);
         int _index = (int)vm->PyInt_AS_C(args[1]);
-        _index = vm->normalizedIndex(_index, _self.size());
+        _index = vm->normalized_index(_index, _self.size());
         return _self[_index];
     });
 
@@ -575,7 +575,6 @@ void __add_module_dis(VM* vm){
     });
 }
 
-
 #define PY_CLASS(mod, name) inline static PyVar _tp(VM* vm) { return vm->_modules[#mod]->attribs[#name]; }
 
 struct ReMatch {
@@ -588,24 +587,18 @@ struct ReMatch {
 
     static PyVar _bind(VM* vm){
         PyVar _tp_match = vm->new_user_type_object(vm->_modules["re"], "Match", vm->_tp_object);
-        vm->bindMethod<0>(_tp_match, "start", [](VM* vm, const pkpy::ArgList& args) {
-            return vm->PyInt(UNION_GET(ReMatch, args[0]).start);
-        });
-
-        vm->bindMethod<0>(_tp_match, "end", [](VM* vm, const pkpy::ArgList& args) {
-            return vm->PyInt(UNION_GET(ReMatch, args[0]).end);
-        });
+        vm->bindMethod<0>(_tp_match, "start", CPP_LAMBDA(vm->PyInt(UNION_GET(ReMatch, args[0]).start)));
+        vm->bindMethod<0>(_tp_match, "end", CPP_LAMBDA(vm->PyInt(UNION_GET(ReMatch, args[0]).end)));
 
         vm->bindMethod<0>(_tp_match, "span", [](VM* vm, const pkpy::ArgList& args) {
             auto& m = UNION_GET(ReMatch, args[0]);
-            PyVarList vec = { vm->PyInt(m.start), vm->PyInt(m.end) };
-            return vm->PyTuple(vec);
+            return vm->PyTuple({ vm->PyInt(m.start), vm->PyInt(m.end) });
         });
 
         vm->bindMethod<1>(_tp_match, "group", [](VM* vm, const pkpy::ArgList& args) {
             auto& m = UNION_GET(ReMatch, args[0]);
             int index = (int)vm->PyInt_AS_C(args[1]);
-            index = vm->normalizedIndex(index, m.m.size());
+            index = vm->normalized_index(index, m.m.size());
             return vm->PyStr(m.m[index].str());
         });
         return _tp_match;
@@ -772,13 +765,15 @@ extern "C" {
         __add_module_math(vm);
         __add_module_re(vm);
         __add_module_dis(vm);
+        
+
+        vm->new_module("ffi");
 
         // add builtins | no exception handler | must succeed
         _Code code = vm->compile(__BUILTINS_CODE, "<builtins>", EXEC_MODE);
         vm->_exec(code, vm->builtins, pkpy::make_shared<PyVarDict>());
 
         pkpy_vm_add_module(vm, "random", __RANDOM_CODE);
-        pkpy_vm_add_module(vm, "os", __OS_CODE);
     }
 
     __EXPORT
diff --git a/src/vm.h b/src/vm.h
index 2901cc8d..57a22d24 100644
--- a/src/vm.h
+++ b/src/vm.h
@@ -700,7 +700,7 @@ public:
         return nullptr;
     }
 
-    int normalizedIndex(int index, int size){
+    int normalized_index(int index, int size){
         if(index < 0) index += size;
         if(index < 0 || index >= size){
             indexError("index out of range, " + std::to_string(index) + " not in [0, " + std::to_string(size) + ")");
diff --git a/tests/_math.py b/tests/_math.py
index b10dd8da..535b8727 100644
--- a/tests/_math.py
+++ b/tests/_math.py
@@ -1,4 +1,7 @@
-from math import log, log10, log2, sin, cos, tan, e, pi, isclose, isnan, isinf
+from math import log, log10, log2, sin, cos, tan, e, pi, isnan, isinf
+
+def isclose(a, b):
+    return abs(a-b) < 0.000001
 
 assert isclose(e, 2.718281828459045)
 assert isclose(pi, 3.141592653589793)
diff --git a/tests/_os_path.py b/tests/_os_path.py
deleted file mode 100644
index be60babf..00000000
--- a/tests/_os_path.py
+++ /dev/null
@@ -1,12 +0,0 @@
-import os
-
-# test os.path.join
-
-f = os.path.join
-
-assert f('/', 'a') == '/a'
-assert f('/', 'a/', 'b/') == '/a/b/'
-assert f('c', 'd') == 'c/d'
-assert f('C:\\', 'a') == 'C:/a'
-assert f('C:\\', 'a\\', 'b\\') == 'C:/a/b/'
-assert f('c\\', 'd/') == 'c/d/'
\ No newline at end of file