X-Git-Url: https://wannabe.guru.org/gitweb/?a=blobdiff_plain;f=file_utils.py;h=7270e30b1fe1513746aaf986e87269968787e842;hb=c46018e2b1ddc78f9df557c3fb24d2c2c849f054;hp=464b0e76cfba0ef4e80ba5343c24bf433584b9b5;hpb=97fbe845e5dfdbda22521117c1783e1fd8515952;p=python_utils.git

diff --git a/file_utils.py b/file_utils.py
index 464b0e7..7270e30 100644
--- a/file_utils.py
+++ b/file_utils.py
@@ -7,11 +7,14 @@ import errno
 import hashlib
 import logging
 import os
+import io
 import pathlib
 import time
 from typing import Optional
 import glob
 from os.path import isfile, join, exists
+from uuid import uuid4
+
 
 logger = logging.getLogger(__name__)
 
@@ -47,26 +50,48 @@ def create_path_if_not_exist(path, on_error=None):
 
 
 def does_file_exist(filename: str) -> bool:
+    """Returns True if a file exists and is a normal file.
+
+    >>> does_file_exist(__file__)
+    True
+    """
     return os.path.exists(filename) and os.path.isfile(filename)
 
 
 def does_directory_exist(dirname: str) -> bool:
+    """Returns True if a file exists and is a directory.
+
+    >>> does_directory_exist('/tmp')
+    True
+    """
     return os.path.exists(dirname) and os.path.isdir(dirname)
 
 
 def does_path_exist(pathname: str) -> bool:
+    """Just a more verbose wrapper around os.path.exists."""
     return os.path.exists(pathname)
 
 
 def get_file_size(filename: str) -> int:
+    """Returns the size of a file in bytes."""
     return os.path.getsize(filename)
 
 
 def is_normal_file(filename: str) -> bool:
+    """Returns True if filename is a normal file.
+
+    >>> is_normal_file(__file__)
+    True
+    """
     return os.path.isfile(filename)
 
 
 def is_directory(filename: str) -> bool:
+    """Returns True if filename is a directory.
+
+    >>> is_directory('/tmp')
+    True
+    """
     return os.path.isdir(filename)
 
 
@@ -249,3 +274,30 @@ def get_files_recursive(directory: str):
     for subdir in get_directories(directory):
         for file_or_directory in get_files_recursive(subdir):
             yield file_or_directory
+
+
+class FileWriter(object):
+    def __init__(self, filename: str) -> None:
+        self.filename = filename
+        uuid = uuid4()
+        self.tempfile = f'{filename}-{uuid}.tmp'
+        self.handle = None
+
+    def __enter__(self) -> io.TextIOWrapper:
+        assert not does_path_exist(self.tempfile)
+        self.handle = open(self.tempfile, mode="w")
+        return self.handle
+
+    def __exit__(self, exc_type, exc_val, exc_tb) -> bool:
+        if self.handle is not None:
+            self.handle.close()
+            cmd = f'/bin/mv -f {self.tempfile} {self.filename}'
+            ret = os.system(cmd)
+            if (ret >> 8) != 0:
+                raise Exception(f'{cmd} failed, exit value {ret>>8}')
+        return None
+
+
+if __name__ == '__main__':
+    import doctest
+    doctest.testmod()