Import ctypes only when necessary

Closes #4541

yt_dlp/cookies.py

@@ -1,6 +1,5 @@
 import base64
 import contextlib
-import ctypes
 import http.cookiejar
 import json
 import os
@@ -876,10 +875,12 @@ def _decrypt_windows_dpapi(ciphertext, logger):
     References:
         - https://docs.microsoft.com/en-us/windows/win32/api/dpapi/nf-dpapi-cryptunprotectdata
     """
-    from ctypes.wintypes import DWORD
+
+    import ctypes
+    import ctypes.wintypes
 
     class DATA_BLOB(ctypes.Structure):
-        _fields_ = [('cbData', DWORD),
+        _fields_ = [('cbData', ctypes.wintypes.DWORD),
                     ('pbData', ctypes.POINTER(ctypes.c_char))]
 
     buffer = ctypes.create_string_buffer(ciphertext)

yt_dlp/utils.py

@@ -6,7 +6,6 @@ import calendar
 import codecs
 import collections
 import contextlib
-import ctypes
 import datetime
 import email.header
 import email.utils
@@ -1983,6 +1982,7 @@ class LockingUnsupportedError(OSError):
 
 # Cross-platform file locking
 if sys.platform == 'win32':
+    import ctypes
     import ctypes.wintypes
     import msvcrt
 
@@ -2362,9 +2362,10 @@ def fix_xml_ampersands(xml_str):
 def setproctitle(title):
     assert isinstance(title, str)
 
-    # ctypes in Jython is not complete
-    # http://bugs.jython.org/issue2148
-    if sys.platform.startswith('java'):
+    # Workaround for https://github.com/yt-dlp/yt-dlp/issues/4541
+    try:
+        import ctypes
+    except ImportError:
         return
 
     try: