Issue #25523: Correct "a" article to "an" article

This changes the main documentation, doc strings, source code comments, and a
couple error messages in the test suite. In some cases the word was removed
or edited some other way to fix the grammar.

26 files changed, 38 insertions, 38 deletions

diff --git a/Doc/library/chunk.rst b/Doc/library/chunk.rst
index 50b6979..a90e9f8 100644
--- a/Doc/library/chunk.rst
+++ b/Doc/library/chunk.rst
@@ -47,7 +47,7 @@ Usually an IFF-type file consists of one or more chunks.  The proposed usage of
 the :class:`Chunk` class defined here is to instantiate an instance at the start
 of each chunk and read from the instance until it reaches the end, after which a
 new instance can be instantiated. At the end of the file, creating a new
-instance will fail with a :exc:`EOFError` exception.
+instance will fail with an :exc:`EOFError` exception.
 
 
 .. class:: Chunk(file, align=True, bigendian=True, inclheader=False)
diff --git a/Doc/library/concurrent.futures.rst b/Doc/library/concurrent.futures.rst
index cc8b335..e63e741 100644
--- a/Doc/library/concurrent.futures.rst
+++ b/Doc/library/concurrent.futures.rst
@@ -81,7 +81,7 @@ Executor Objects
 ThreadPoolExecutor
 ------------------
 
-:class:`ThreadPoolExecutor` is a :class:`Executor` subclass that uses a pool of
+:class:`ThreadPoolExecutor` is an :class:`Executor` subclass that uses a pool of
 threads to execute calls asynchronously.
 
 Deadlocks can occur when the callable associated with a :class:`Future` waits on
@@ -285,7 +285,7 @@ The :class:`Future` class encapsulates the asynchronous execution of a callable.
 
        Added callables are called in the order that they were added and are
        always called in a thread belonging to the process that added them.  If
-       the callable raises a :exc:`Exception` subclass, it will be logged and
+       the callable raises an :exc:`Exception` subclass, it will be logged and
        ignored.  If the callable raises a :exc:`BaseException` subclass, the
        behavior is undefined.
 
diff --git a/Doc/library/ctypes.rst b/Doc/library/ctypes.rst
index 588ac7c..630d279 100644
--- a/Doc/library/ctypes.rst
+++ b/Doc/library/ctypes.rst
@@ -39,7 +39,7 @@ loads libraries which export functions using the standard ``cdecl`` calling
 convention, while *windll* libraries call functions using the ``stdcall``
 calling convention. *oledll* also uses the ``stdcall`` calling convention, and
 assumes the functions return a Windows :c:type:`HRESULT` error code. The error
-code is used to automatically raise a :class:`OSError` exception when the
+code is used to automatically raise an :class:`OSError` exception when the
 function call fails.
 
 .. versionchanged:: 3.3
diff --git a/Doc/library/difflib.rst b/Doc/library/difflib.rst
index 6092582..cead818 100644
--- a/Doc/library/difflib.rst
+++ b/Doc/library/difflib.rst
@@ -269,7 +269,7 @@ diffs. For comparing directories and files, see also, the :mod:`filecmp` module.
    generating the delta lines) in unified diff format.
 
    Unified diffs are a compact way of showing just the lines that have changed plus
-   a few lines of context.  The changes are shown in a inline style (instead of
+   a few lines of context.  The changes are shown in an inline style (instead of
    separate before/after blocks).  The number of context lines is set by *n* which
    defaults to three.
 
diff --git a/Doc/library/fcntl.rst b/Doc/library/fcntl.rst
index 8e932fb..a517d6e 100644
--- a/Doc/library/fcntl.rst
+++ b/Doc/library/fcntl.rst
@@ -16,13 +16,13 @@ interface to the :c:func:`fcntl` and :c:func:`ioctl` Unix routines.
 
 All functions in this module take a file descriptor *fd* as their first
 argument.  This can be an integer file descriptor, such as returned by
-``sys.stdin.fileno()``, or a :class:`io.IOBase` object, such as ``sys.stdin``
+``sys.stdin.fileno()``, or an :class:`io.IOBase` object, such as ``sys.stdin``
 itself, which provides a :meth:`~io.IOBase.fileno` that returns a genuine file
 descriptor.
 
 .. versionchanged:: 3.3
-   Operations in this module used to raise a :exc:`IOError` where they now
-   raise a :exc:`OSError`.
+   Operations in this module used to raise an :exc:`IOError` where they now
+   raise an :exc:`OSError`.
 
 
 The module defines the following functions:
diff --git a/Doc/library/ftplib.rst b/Doc/library/ftplib.rst
index 3b9f50c..2521f49 100644
--- a/Doc/library/ftplib.rst
+++ b/Doc/library/ftplib.rst
@@ -287,9 +287,9 @@ followed by ``lines`` for the text version or ``binary`` for the binary version.
 
 .. method:: FTP.transfercmd(cmd, rest=None)
 
-   Initiate a transfer over the data connection.  If the transfer is active, send a
+   Initiate a transfer over the data connection.  If the transfer is active, send an
    ``EPRT`` or  ``PORT`` command and the transfer command specified by *cmd*, and
-   accept the connection.  If the server is passive, send a ``EPSV`` or ``PASV``
+   accept the connection.  If the server is passive, send an ``EPSV`` or ``PASV``
    command, connect to it, and start the transfer command.  Either way, return the
    socket for the connection.
 
diff --git a/Doc/library/functions.rst b/Doc/library/functions.rst
index 97c9f8d..1261062 100644
--- a/Doc/library/functions.rst
+++ b/Doc/library/functions.rst
@@ -1029,9 +1029,9 @@ are always available.  They are listed here in alphabetical order.
    :class:`io.TextIOBase` (specifically :class:`io.TextIOWrapper`).  When used
    to open a file in a binary mode with buffering, the returned class is a
    subclass of :class:`io.BufferedIOBase`.  The exact class varies: in read
-   binary mode, it returns a :class:`io.BufferedReader`; in write binary and
-   append binary modes, it returns a :class:`io.BufferedWriter`, and in
-   read/write mode, it returns a :class:`io.BufferedRandom`.  When buffering is
+   binary mode, it returns an :class:`io.BufferedReader`; in write binary and
+   append binary modes, it returns an :class:`io.BufferedWriter`, and in
+   read/write mode, it returns an :class:`io.BufferedRandom`.  When buffering is
    disabled, the raw stream, a subclass of :class:`io.RawIOBase`,
    :class:`io.FileIO`, is returned.
 
diff --git a/Doc/library/gzip.rst b/Doc/library/gzip.rst
index 78536fa..ce02077 100644
--- a/Doc/library/gzip.rst
+++ b/Doc/library/gzip.rst
@@ -100,7 +100,7 @@ The module defines the following items:
 
    Calling a :class:`GzipFile` object's :meth:`close` method does not close
    *fileobj*, since you might wish to append more material after the compressed
-   data.  This also allows you to pass a :class:`io.BytesIO` object opened for
+   data.  This also allows you to pass an :class:`io.BytesIO` object opened for
    writing as *fileobj*, and retrieve the resulting memory buffer using the
    :class:`io.BytesIO` object's :meth:`~io.BytesIO.getvalue` method.
 
diff --git a/Doc/library/http.cookiejar.rst b/Doc/library/http.cookiejar.rst
index 30648ac..ca68aac 100644
--- a/Doc/library/http.cookiejar.rst
+++ b/Doc/library/http.cookiejar.rst
@@ -176,7 +176,7 @@ contained :class:`Cookie` objects.
 
    The *response* object (usually the result of a call to
    :meth:`urllib.request.urlopen`, or similar) should support an :meth:`info`
-   method, which returns a :class:`email.message.Message` instance.
+   method, which returns an :class:`email.message.Message` instance.
 
    The *request* object (usually a :class:`urllib.request.Request` instance)
    must support the methods :meth:`get_full_url`, :meth:`get_host`,
diff --git a/Doc/library/http.server.rst b/Doc/library/http.server.rst
index 1c3e202..0bde35b 100644
--- a/Doc/library/http.server.rst
+++ b/Doc/library/http.server.rst
@@ -176,7 +176,7 @@ of which this module provides three different variants:
 
    .. method:: handle_expect_100()
 
-      When a HTTP/1.1 compliant server receives a ``Expect: 100-continue``
+      When a HTTP/1.1 compliant server receives an ``Expect: 100-continue``
       request header it responds back with a ``100 Continue`` followed by ``200
       OK`` headers.
       This method can be overridden to raise an error if the server does not
@@ -210,7 +210,7 @@ of which this module provides three different variants:
       are picked up from the :meth:`version_string` and
       :meth:`date_time_string` methods, respectively. If the server does not
       intend to send any other headers using the :meth:`send_header` method,
-      then :meth:`send_response` should be followed by a :meth:`end_headers`
+      then :meth:`send_response` should be followed by an :meth:`end_headers`
       call.
 
       .. versionchanged:: 3.3
diff --git a/Doc/library/mailbox.rst b/Doc/library/mailbox.rst
index 6334bd6..d29902d 100644
--- a/Doc/library/mailbox.rst
+++ b/Doc/library/mailbox.rst
@@ -674,7 +674,7 @@ Supported mailbox formats are Maildir, mbox, MH, Babyl, and MMDF.
 
       In Babyl mailboxes, the headers of a message are not stored contiguously
       with the body of the message. To generate a file-like representation, the
-      headers and body are copied together into a :class:`io.BytesIO` instance,
+      headers and body are copied together into an :class:`io.BytesIO` instance,
       which has an API identical to that of a
       file. As a result, the file-like object is truly independent of the
       underlying mailbox but does not save memory compared to a string
diff --git a/Doc/library/multiprocessing.rst b/Doc/library/multiprocessing.rst
index 3ffb7f9..f7dc11b 100644
--- a/Doc/library/multiprocessing.rst
+++ b/Doc/library/multiprocessing.rst
@@ -1041,7 +1041,7 @@ Connection objects are usually created using :func:`Pipe` -- see also
       readable.
 
       .. versionchanged:: 3.3
-         This function used to raise a :exc:`IOError`, which is now an
+         This function used to raise :exc:`IOError`, which is now an
          alias of :exc:`OSError`.
 
 
diff --git a/Doc/library/nntplib.rst b/Doc/library/nntplib.rst
index 3943f2c..4797965 100644
--- a/Doc/library/nntplib.rst
+++ b/Doc/library/nntplib.rst
@@ -341,7 +341,7 @@ tuples or objects that the method normally returns will be empty.
 
 .. method:: NNTP.over(message_spec, *, file=None)
 
-   Send a ``OVER`` command, or a ``XOVER`` command on legacy servers.
+   Send an ``OVER`` command, or an ``XOVER`` command on legacy servers.
    *message_spec* can be either a string representing a message id, or
    a ``(first, last)`` tuple of numbers indicating a range of articles in
    the current group, or a ``(first, None)`` tuple indicating a range of
diff --git a/Doc/library/optparse.rst b/Doc/library/optparse.rst
index 72145aa..160c29d 100644
--- a/Doc/library/optparse.rst
+++ b/Doc/library/optparse.rst
@@ -1324,7 +1324,7 @@ where the input parameters are
    the list of arguments to process (default: ``sys.argv[1:]``)
 
 ``values``
-   a :class:`optparse.Values` object to store option arguments in (default: a
+   an :class:`optparse.Values` object to store option arguments in (default: a
    new instance of :class:`Values`) -- if you give an existing object, the
    option defaults will not be initialized on it
 
diff --git a/Doc/library/os.path.rst b/Doc/library/os.path.rst
index 92631b2..33ef564 100644
--- a/Doc/library/os.path.rst
+++ b/Doc/library/os.path.rst
@@ -263,7 +263,7 @@ the :mod:`glob` module.)
 
    Return ``True`` if both pathname arguments refer to the same file or directory.
    This is determined by the device number and i-node number and raises an
-   exception if a :func:`os.stat` call on either pathname fails.
+   exception if an :func:`os.stat` call on either pathname fails.
 
    Availability: Unix, Windows.
 
diff --git a/Doc/library/pickle.rst b/Doc/library/pickle.rst
index 25a9240..08618fa 100644
--- a/Doc/library/pickle.rst
+++ b/Doc/library/pickle.rst
@@ -221,7 +221,7 @@ process more convenient:
    The argument *file* must have two methods, a read() method that takes an
    integer argument, and a readline() method that requires no arguments.  Both
    methods should return bytes.  Thus *file* can be an on-disk file opened for
-   binary reading, a :class:`io.BytesIO` object, or any other custom object
+   binary reading, an :class:`io.BytesIO` object, or any other custom object
    that meets this interface.
 
    Optional keyword arguments are *fix_imports*, *encoding* and *errors*,
@@ -357,7 +357,7 @@ The :mod:`pickle` module exports two classes, :class:`Pickler` and
    The argument *file* must have two methods, a read() method that takes an
    integer argument, and a readline() method that requires no arguments.  Both
    methods should return bytes.  Thus *file* can be an on-disk file object
-   opened for binary reading, a :class:`io.BytesIO` object, or any other
+   opened for binary reading, an :class:`io.BytesIO` object, or any other
    custom object that meets this interface.
 
    Optional keyword arguments are *fix_imports*, *encoding* and *errors*,
diff --git a/Doc/library/pyexpat.rst b/Doc/library/pyexpat.rst
index 78aa99c..620ffb1 100644
--- a/Doc/library/pyexpat.rst
+++ b/Doc/library/pyexpat.rst
@@ -763,7 +763,7 @@ The ``errors`` module has the following attributes:
 
 .. data:: XML_ERROR_UNDEFINED_ENTITY
 
-   A reference was made to a entity which was not defined.
+   A reference was made to an entity which was not defined.
 
 
 .. data:: XML_ERROR_UNKNOWN_ENCODING
diff --git a/Doc/library/shutil.rst b/Doc/library/shutil.rst
index 2606fed..7566521 100644
--- a/Doc/library/shutil.rst
+++ b/Doc/library/shutil.rst
@@ -206,8 +206,8 @@ Directory and files operations
    and metadata of the linked files are copied to the new tree.
 
    When *symlinks* is false, if the file pointed by the symlink doesn't
-   exist, a exception will be added in the list of errors raised in
-   a :exc:`Error` exception at the end of the copy process.
+   exist, an exception will be added in the list of errors raised in
+   an :exc:`Error` exception at the end of the copy process.
    You can set the optional *ignore_dangling_symlinks* flag to true if you
    want to silence this exception. Notice that this option has no effect
    on platforms that don't support :func:`os.symlink`.
diff --git a/Doc/library/smtplib.rst b/Doc/library/smtplib.rst
index 8e1bfb5..b87ad5f 100644
--- a/Doc/library/smtplib.rst
+++ b/Doc/library/smtplib.rst
@@ -22,7 +22,7 @@ Protocol) and :rfc:`1869` (SMTP Service Extensions).
 
 .. class:: SMTP(host='', port=0, local_hostname=None[, timeout], source_address=None)
 
-   A :class:`SMTP` instance encapsulates an SMTP connection.  It has methods
+   An :class:`SMTP` instance encapsulates an SMTP connection.  It has methods
    that support a full repertoire of SMTP and ESMTP operations. If the optional
    host and port parameters are given, the SMTP :meth:`connect` method is
    called with those parameters during initialization.  If specified,
@@ -65,7 +65,7 @@ Protocol) and :rfc:`1869` (SMTP Service Extensions).
                     certfile=None [, timeout], context=None, \
                     source_address=None)
 
-   A :class:`SMTP_SSL` instance behaves exactly the same as instances of
+   An :class:`SMTP_SSL` instance behaves exactly the same as instances of
    :class:`SMTP`. :class:`SMTP_SSL` should be used for situations where SSL is
    required from the beginning of the connection and using :meth:`starttls` is
    not appropriate. If *host* is not specified, the local host is used. If
diff --git a/Doc/library/socket.rst b/Doc/library/socket.rst
index 638a77e..80d5811 100644
--- a/Doc/library/socket.rst
+++ b/Doc/library/socket.rst
@@ -693,7 +693,7 @@ The :mod:`socket` module also offers various network-related services:
 
    Supported values for *address_family* are currently :const:`AF_INET` and
    :const:`AF_INET6`. If the string *packed_ip* is not the correct length for the
-   specified address family, :exc:`ValueError` will be raised.  A
+   specified address family, :exc:`ValueError` will be raised.
    :exc:`OSError` is raised for errors from the call to :func:`inet_ntop`.
 
    Availability: Unix (maybe not all platforms), Windows.
@@ -969,7 +969,7 @@ to sockets.
    interpreted the same way as by the built-in :func:`open` function.
 
    The socket must be in blocking mode; it can have a timeout, but the file
-   object's internal buffer may end up in a inconsistent state if a timeout
+   object's internal buffer may end up in an inconsistent state if a timeout
    occurs.
 
    Closing the file object returned by :meth:`makefile` won't close the
diff --git a/Doc/library/sqlite3.rst b/Doc/library/sqlite3.rst
index 6097e7a..715321a 100644
--- a/Doc/library/sqlite3.rst
+++ b/Doc/library/sqlite3.rst
@@ -615,7 +615,7 @@ Cursor Objects
    .. attribute:: lastrowid
 
       This read-only attribute provides the rowid of the last modified row. It is
-      only set if you issued a ``INSERT`` statement using the :meth:`execute`
+      only set if you issued an ``INSERT`` statement using the :meth:`execute`
       method. For operations other than ``INSERT`` or when :meth:`executemany` is
       called, :attr:`lastrowid` is set to :const:`None`.
 
diff --git a/Doc/library/stdtypes.rst b/Doc/library/stdtypes.rst
index ce3c532..fdb5e9e 100644
--- a/Doc/library/stdtypes.rst
+++ b/Doc/library/stdtypes.rst
@@ -951,7 +951,7 @@ Notes:
    runtime cost, you must switch to one of the alternatives below:
 
    * if concatenating :class:`str` objects, you can build a list and use
-     :meth:`str.join` at the end or else write to a :class:`io.StringIO`
+     :meth:`str.join` at the end or else write to an :class:`io.StringIO`
      instance and retrieve its value when complete
 
    * if concatenating :class:`bytes` objects, you can similarly use
diff --git a/Doc/library/sunau.rst b/Doc/library/sunau.rst
index a94ae08..bd37ee2 100644
--- a/Doc/library/sunau.rst
+++ b/Doc/library/sunau.rst
@@ -54,8 +54,8 @@ The :mod:`sunau` module defines the following functions:
 
    Note that it does not allow read/write files.
 
-   A *mode* of ``'r'`` returns a :class:`AU_read` object, while a *mode* of ``'w'``
-   or ``'wb'`` returns a :class:`AU_write` object.
+   A *mode* of ``'r'`` returns an :class:`AU_read` object, while a *mode* of ``'w'``
+   or ``'wb'`` returns an :class:`AU_write` object.
 
 
 .. function:: openfp(file, mode)
diff --git a/Doc/library/tempfile.rst b/Doc/library/tempfile.rst
index 44d025d..1efb5e6 100644
--- a/Doc/library/tempfile.rst
+++ b/Doc/library/tempfile.rst
@@ -82,7 +82,7 @@ The module defines the following user-callable items:
    causes the file to roll over to an on-disk file regardless of its size.
 
    The returned object is a file-like object whose :attr:`_file` attribute
-   is either a :class:`io.BytesIO` or :class:`io.StringIO` object (depending on
+   is either an :class:`io.BytesIO` or :class:`io.StringIO` object (depending on
    whether binary or text *mode* was specified) or a true file
    object, depending on whether :func:`rollover` has been called.  This
    file-like object can be used in a :keyword:`with` statement, just like
diff --git a/Doc/library/unittest.mock.rst b/Doc/library/unittest.mock.rst
index 48eefe9..d7d735c 100644
--- a/Doc/library/unittest.mock.rst
+++ b/Doc/library/unittest.mock.rst
@@ -1105,7 +1105,7 @@ you wanted a :class:`NonCallableMock` to be used:
       ...
     TypeError: 'NonCallableMock' object is not callable
 
-Another use case might be to replace an object with a :class:`io.StringIO` instance:
+Another use case might be to replace an object with an :class:`io.StringIO` instance:
 
     >>> from io import StringIO
     >>> def foo():
diff --git a/Doc/library/xml.dom.pulldom.rst b/Doc/library/xml.dom.pulldom.rst
index a9c9f67..a3b8bc1 100644
--- a/Doc/library/xml.dom.pulldom.rst
+++ b/Doc/library/xml.dom.pulldom.rst
@@ -47,7 +47,7 @@ Example::
 * :data:`PROCESSING_INSTRUCTION`
 * :data:`IGNORABLE_WHITESPACE`
 
-``node`` is a object of type :class:`xml.dom.minidom.Document`,
+``node`` is an object of type :class:`xml.dom.minidom.Document`,
 :class:`xml.dom.minidom.Element` or :class:`xml.dom.minidom.Text`.
 
 Since the document is treated as a "flat" stream of events, the document "tree"