X-Git-Url: https://wannabe.guru.org/gitweb/?a=blobdiff_plain;ds=sidebyside;f=string_utils.py;h=a766adabe97ffc8432a9bda280c66107634bc52b;hb=1ee64f3522abbbc2df154c8f44be87929a16e17e;hp=d75c6ba1aca2c559ed4254d535747c54f4719bf5;hpb=e8fbbb7306430478dec55d2c963eed116d8330cc;p=python_utils.git

diff --git a/string_utils.py b/string_utils.py
index d75c6ba..a766ada 100644
--- a/string_utils.py
+++ b/string_utils.py
@@ -40,7 +40,17 @@ import string
 import unicodedata
 import warnings
 from itertools import zip_longest
-from typing import Any, Callable, Dict, Iterable, List, Optional, Sequence, Tuple
+from typing import (
+    Any,
+    Callable,
+    Dict,
+    Iterable,
+    List,
+    Literal,
+    Optional,
+    Sequence,
+    Tuple,
+)
 from uuid import uuid4
 
 import list_utils
@@ -1208,7 +1218,7 @@ def sprintf(*args, **kwargs) -> str:
     return ret
 
 
-class SprintfStdout(object):
+class SprintfStdout(contextlib.AbstractContextManager):
     """
     A context manager that captures outputs to stdout.
 
@@ -1228,10 +1238,10 @@ class SprintfStdout(object):
         self.recorder.__enter__()
         return lambda: self.destination.getvalue()
 
-    def __exit__(self, *args) -> None:
+    def __exit__(self, *args) -> Literal[False]:
         self.recorder.__exit__(*args)
         self.destination.seek(0)
-        return None  # don't suppress exceptions
+        return False
 
 
 def capitalize_first_letter(txt: str) -> str:
@@ -1639,7 +1649,7 @@ def ip_v4_sort_key(txt: str) -> Optional[Tuple[int, ...]]:
     if not is_ip_v4(txt):
         print(f"not IP: {txt}")
         return None
-    return tuple([int(x) for x in txt.split('.')])
+    return tuple(int(x) for x in txt.split('.'))
 
 
 def path_ancestors_before_descendants_sort_key(volume: str) -> Tuple[str, ...]:
@@ -1654,7 +1664,7 @@ def path_ancestors_before_descendants_sort_key(volume: str) -> Tuple[str, ...]:
     ['/usr', '/usr/local', '/usr/local/bin']
 
     """
-    return tuple([x for x in volume.split('/') if len(x) > 0])
+    return tuple(x for x in volume.split('/') if len(x) > 0)
 
 
 def replace_all(in_str: str, replace_set: str, replacement: str) -> str:
@@ -1670,6 +1680,20 @@ def replace_all(in_str: str, replace_set: str, replacement: str) -> str:
     return in_str
 
 
+def replace_nth(string: str, source: str, target: str, nth: int):
+    """Replaces the nth occurrance of a substring within a string.
+
+    >>> replace_nth('this is a test', ' ', '-', 3)
+    'this is a-test'
+
+    """
+    where = [m.start() for m in re.finditer(source, string)][nth - 1]
+    before = string[:where]
+    after = string[where:]
+    after = after.replace(source, target, 1)
+    return before + after
+
+
 if __name__ == '__main__':
     import doctest