diff --git a/README.md b/README.md
index db63ab8..af0d56d 100644
--- a/README.md
+++ b/README.md
@@ -53,12 +53,11 @@ from ioutil import File
 data = [{'a': 1, 'b': 2}, {'a': 3, 'b': 4}]
 path = '.../file.csv'
 
-csv = File.getinstance('csv')
-csv.write(data=data, path=path)  # to write csv
-csv.read(path=path)  # to read csv
+File.write(data=data, path=path)  # to write file
+File.read(path=path)  # to read file
 ```
 
-### Command Line (not recommended) 
+### Command Line (not recommended)
 
 To write a text file.
 
diff --git a/ioutil/__init__.py b/ioutil/__init__.py
index 684612e..a7f8963 100644
--- a/ioutil/__init__.py
+++ b/ioutil/__init__.py
@@ -1,6 +1,8 @@
 """to read and write files"""
-
-from typing import Literal
+from __future__ import annotations
+import os
+from srutil import util
+from typing import Literal, Any, AnyStr
 
 from ioutil._file import _File
 from ioutil._csv import Csv
@@ -9,14 +11,42 @@
 from ioutil._json import Json
 from ioutil._parquet import Parquet
 
+_FS = Literal["csv", "json", "parquet", "toml", "text"]
+
 
 class File:
     @staticmethod
-    def getinstance(_format: Literal["csv", "json", "parquet", "toml", "text"]) -> _File:
-        _instance = {"csv": Csv, "json": Json, "parquet": Parquet, "toml": TOML, "text": Text}.get(_format)
-        if not _instance:
-            _instance = _File
-        return _instance()
+    def __getinstance(path: AnyStr | os.PathLike = None, _format: _FS = None) -> _File:
+        if path and not _format:
+            ext = list(os.path.splitext(path)).pop()
+            _format = {".csv": "csv", ".json": "json", ".parquet": ".parquet", ".toml": "toml", ".txt": "text"}.get(ext)
+        if _format:
+            _instance = {"csv": Csv, "json": Json, "parquet": Parquet, "toml": TOML, "text": Text}.get(_format)
+            return _instance()
+        else:
+            raise ValueError("Invalid file type")
+
+    @staticmethod
+    def __remove_unwanted_params(f: _File, params: dict) -> dict:
+        method_list = {'read': f.read, 'write': f.write}
+        params_of_method = util.paramsofmethod(method_list.get(util.whocalledme())).keys()
+        new_params = dict()
+        for key, value in params.items():
+            if key in params_of_method:
+                new_params.setdefault(key, value)
+        return new_params
+
+    @staticmethod
+    def read(path: AnyStr | os.PathLike, _format: _FS = None, **kwargs) -> Any:
+        f = File.__getinstance(path=path, _format=_format)
+        kwargs = File.__remove_unwanted_params(f, kwargs)
+        return f.read(path=path, **kwargs)
+
+    @staticmethod
+    def write(data, path: AnyStr | os.PathLike, _format: _FS = None, **kwargs) -> bool:
+        f = File.__getinstance(path=path, _format=_format)
+        kwargs = File.__remove_unwanted_params(f, kwargs)
+        return f.write(data=data, path=path, **kwargs)
 
 
 csv = Csv()
@@ -26,7 +56,7 @@ def getinstance(_format: Literal["csv", "json", "parquet", "toml", "text"]) -> _
 toml = TOML()
 
 __author__ = 'srg'
-__version__ = '1.0.2'
+__version__ = '1.0.3'
 
 __all__ = [
     'File',
diff --git a/ioutil/__main__.py b/ioutil/__main__.py
index f6109bb..3ae625d 100644
--- a/ioutil/__main__.py
+++ b/ioutil/__main__.py
@@ -5,10 +5,9 @@
 import sys
 import argparse
 from srutil import util
-from typing import AnyStr, Any
+from typing import Any
 
-from . import File, __version__, __package__, __all__
-from ._file import _File
+from . import File, __version__, __package__
 
 
 def _epilog() -> str:
@@ -33,11 +32,12 @@ def get_argument() -> argparse.Namespace:
     parser.add_argument_group(group)
     options = parser.parse_args()
     if not options.format:
-        _format = list(os.path.splitext(options.path)).pop().lstrip('.')
-        if _format != 'File' and _format not in __all__:
+        _ext = list(os.path.splitext(options.path)).pop()
+        _format = {".csv": "csv", ".json": "json", ".parquet": ".parquet", ".toml": "toml", ".txt": "text"}
+        if _ext not in _format:
             parser.error("the following arguments are required: -f/--format")
         else:
-            options.format = _format
+            options.format = _format.get(_ext)
     if not options.read and not options.write:
         parser.error("one of the following arguments are required: -r/--read or -w/--write")
     if options.read and options.write:
@@ -47,41 +47,18 @@ def get_argument() -> argparse.Namespace:
     return options
 
 
-def _remove_unwanted_params(f: _File, params: dict) -> dict:
-    method_list = {'read': f.read, 'write': f.write}
-    params_of_method = util.paramsofmethod(method_list.get(util.whocalledme())).keys()
-    new_params = dict()
-    for key, value in params.items():
-        if key in params_of_method:
-            new_params.setdefault(key, value)
-    return new_params
-
-
 def _get_data(_data: str, _format: str) -> Any:
     return _data if _format == 'text' else ast.literal_eval(_data)
 
 
-def read(f: _File, path: AnyStr | os.PathLike, **kwargs) -> None:
-    kwargs = _remove_unwanted_params(f, kwargs)
-    data = f.read(path=path, **kwargs)
-    print(data)
-
-
-def write(f: _File, data, path: AnyStr | os.PathLike, **kwargs) -> None:
-    kwargs = _remove_unwanted_params(f, kwargs)
-    status = f.write(data=data, path=path, **kwargs)
-    print(status)
-
-
 def main():
     options = get_argument()
-    f = File.getinstance(options.format)
-    mode = options.mode if options.mode else 'w' if options.write else 'r'
+    mode = options.mode if options.mode else None
     if options.read:
-        read(f, options.path, mode=mode, _rfv=options.rfv)
+        print(File.read(options.path, _format=options.format, mode=mode, _rfv=options.rfv))
     elif options.write:
         data = _get_data(options.data, options.format)
-        write(f, data, options.path, mode=mode)
+        print(File.write(data, options.path, _format=options.format, mode=mode))
 
 
 if __name__ == "__main__":
diff --git a/pyproject.toml b/pyproject.toml
index aa107bd..cfc5091 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "ioutil"
-version = "1.0.2"
+version = "1.0.3"
 description = "To read and write files."
 readme = "README.md"
 requires-python = ">=3.6"