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Doc/library/ftplib.rst
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Miss Islington (bot)
Simple Enhancement. Add missing return statements in ftplib documentation. (GH-25968) (#25970)
07 май 2021, 17:13
07 май 2021, 17:13bf309d7
:mod:`ftplib` --- FTP protocol client
=====================================

.. module:: ftplib
   :synopsis: FTP protocol client (requires sockets).

**Source code:** :source:`Lib/ftplib.py`

.. index::
   pair: FTP; protocol
   single: FTP; ftplib (standard module)

--------------

This module defines the class :class:`FTP` and a few related items. The
:class:`FTP` class implements the client side of the FTP protocol.  You can use
this to write Python programs that perform a variety of automated FTP jobs, such
as mirroring other FTP servers.  It is also used by the module
:mod:`urllib.request` to handle URLs that use FTP.  For more information on FTP
(File Transfer Protocol), see Internet :rfc:`959`.

The default encoding is UTF-8, following :rfc:`2640`.

Here's a sample session using the :mod:`ftplib` module::

   >>> from ftplib import FTP
   >>> ftp = FTP('ftp.us.debian.org')  # connect to host, default port
   >>> ftp.login()                     # user anonymous, passwd anonymous@
   '230 Login successful.'
   >>> ftp.cwd('debian')               # change into "debian" directory
   '250 Directory successfully changed.'
   >>> ftp.retrlines('LIST')           # list directory contents
   -rw-rw-r--    1 1176     1176         1063 Jun 15 10:18 README
   ...
   drwxr-sr-x    5 1176     1176         4096 Dec 19  2000 pool
   drwxr-sr-x    4 1176     1176         4096 Nov 17  2008 project
   drwxr-xr-x    3 1176     1176         4096 Oct 10  2012 tools
   '226 Directory send OK.'
   >>> with open('README', 'wb') as fp:
   >>>     ftp.retrbinary('RETR README', fp.write)
   '226 Transfer complete.'
   >>> ftp.quit()
   '221 Goodbye.'


The module defines the following items:

.. class:: FTP(host='', user='', passwd='', acct='', timeout=None, source_address=None, *, encoding='utf-8')

   Return a new instance of the :class:`FTP` class.  When *host* is given, the
   method call ``connect(host)`` is made.  When *user* is given, additionally
   the method call ``login(user, passwd, acct)`` is made (where *passwd* and
   *acct* default to the empty string when not given).  The optional *timeout*
   parameter specifies a timeout in seconds for blocking operations like the
   connection attempt (if is not specified, the global default timeout setting
   will be used). *source_address* is a 2-tuple ``(host, port)`` for the socket
   to bind to as its source address before connecting. The *encoding* parameter
   specifies the encoding for directories and filenames.

   The :class:`FTP` class supports the :keyword:`with` statement, e.g.:

    >>> from ftplib import FTP
    >>> with FTP("ftp1.at.proftpd.org") as ftp:
    ...     ftp.login()
    ...     ftp.dir()
    ... # doctest: +SKIP
    '230 Anonymous login ok, restrictions apply.'
    dr-xr-xr-x   9 ftp      ftp           154 May  6 10:43 .
    dr-xr-xr-x   9 ftp      ftp           154 May  6 10:43 ..
    dr-xr-xr-x   5 ftp      ftp          4096 May  6 10:43 CentOS
    dr-xr-xr-x   3 ftp      ftp            18 Jul 10  2008 Fedora
    >>>

   .. versionchanged:: 3.2
      Support for the :keyword:`with` statement was added.

   .. versionchanged:: 3.3
      *source_address* parameter was added.

   .. versionchanged:: 3.9
      If the *timeout* parameter is set to be zero, it will raise a
      :class:`ValueError` to prevent the creation of a non-blocking socket.
      The *encoding* parameter was added, and the default was changed from
      Latin-1 to UTF-8 to follow :rfc:`2640`.

.. class:: FTP_TLS(host='', user='', passwd='', acct='', keyfile=None, certfile=None, context=None, timeout=None, source_address=None, *, encoding='utf-8')

   A :class:`FTP` subclass which adds TLS support to FTP as described in
   :rfc:`4217`.
   Connect as usual to port 21 implicitly securing the FTP control connection
   before authenticating. Securing the data connection requires the user to
   explicitly ask for it by calling the :meth:`prot_p` method.  *context*
   is a :class:`ssl.SSLContext` object which allows bundling SSL configuration
   options, certificates and private keys into a single (potentially
   long-lived) structure.  Please read :ref:`ssl-security` for best practices.

   *keyfile* and *certfile* are a legacy alternative to *context* -- they
   can point to PEM-formatted private key and certificate chain files
   (respectively) for the SSL connection.

   .. versionadded:: 3.2

   .. versionchanged:: 3.3
      *source_address* parameter was added.

   .. versionchanged:: 3.4
      The class now supports hostname check with
      :attr:`ssl.SSLContext.check_hostname` and *Server Name Indication* (see
      :data:`ssl.HAS_SNI`).

   .. deprecated:: 3.6

       *keyfile* and *certfile* are deprecated in favor of *context*.
       Please use :meth:`ssl.SSLContext.load_cert_chain` instead, or let
       :func:`ssl.create_default_context` select the system's trusted CA
       certificates for you.

   .. versionchanged:: 3.9
      If the *timeout* parameter is set to be zero, it will raise a
      :class:`ValueError` to prevent the creation of a non-blocking socket.
      The *encoding* parameter was added, and the default was changed from
      Latin-1 to UTF-8 to follow :rfc:`2640`.

   Here's a sample session using the :class:`FTP_TLS` class::

      >>> ftps = FTP_TLS('ftp.pureftpd.org')
      >>> ftps.login()
      '230 Anonymous user logged in'
      >>> ftps.prot_p()
      '200 Data protection level set to "private"'
      >>> ftps.nlst()
      ['6jack', 'OpenBSD', 'antilink', 'blogbench', 'bsdcam', 'clockspeed', 'djbdns-jedi', 'docs', 'eaccelerator-jedi', 'favicon.ico', 'francotone', 'fugu', 'ignore', 'libpuzzle', 'metalog', 'minidentd', 'misc', 'mysql-udf-global-user-variables', 'php-jenkins-hash', 'php-skein-hash', 'php-webdav', 'phpaudit', 'phpbench', 'pincaster', 'ping', 'posto', 'pub', 'public', 'public_keys', 'pure-ftpd', 'qscan', 'qtc', 'sharedance', 'skycache', 'sound', 'tmp', 'ucarp']


.. exception:: error_reply

   Exception raised when an unexpected reply is received from the server.


.. exception:: error_temp

   Exception raised when an error code signifying a temporary error (response
   codes in the range 400--499) is received.


.. exception:: error_perm

   Exception raised when an error code signifying a permanent error (response
   codes in the range 500--599) is received.


.. exception:: error_proto

   Exception raised when a reply is received from the server that does not fit
   the response specifications of the File Transfer Protocol, i.e. begin with a
   digit in the range 1--5.


.. data:: all_errors

   The set of all exceptions (as a tuple) that methods of :class:`FTP`
   instances may raise as a result of problems with the FTP connection (as
   opposed to programming errors made by the caller).  This set includes the
   four exceptions listed above as well as :exc:`OSError` and :exc:`EOFError`.


.. seealso::

   Module :mod:`netrc`
      Parser for the :file:`.netrc` file format.  The file :file:`.netrc` is
      typically used by FTP clients to load user authentication information
      before prompting the user.


.. _ftp-objects:

FTP Objects
-----------

Several methods are available in two flavors: one for handling text files and
another for binary files.  These are named for the command which is used
followed by ``lines`` for the text version or ``binary`` for the binary version.

:class:`FTP` instances have the following methods:


.. method:: FTP.set_debuglevel(level)

   Set the instance's debugging level.  This controls the amount of debugging
   output printed.  The default, ``0``, produces no debugging output.  A value of
   ``1`` produces a moderate amount of debugging output, generally a single line
   per request.  A value of ``2`` or higher produces the maximum amount of
   debugging output, logging each line sent and received on the control connection.


.. method:: FTP.connect(host='', port=0, timeout=None, source_address=None)

   Connect to the given host and port.  The default port number is ``21``, as
   specified by the FTP protocol specification.  It is rarely needed to specify a
   different port number.  This function should be called only once for each
   instance; it should not be called at all if a host was given when the instance
   was created.  All other methods can only be used after a connection has been
   made.
   The optional *timeout* parameter specifies a timeout in seconds for the
   connection attempt. If no *timeout* is passed, the global default timeout
   setting will be used.
   *source_address* is a 2-tuple ``(host, port)`` for the socket to bind to as
   its source address before connecting.

   .. audit-event:: ftplib.connect self,host,port ftplib.FTP.connect

   .. versionchanged:: 3.3
      *source_address* parameter was added.


.. method:: FTP.getwelcome()

   Return the welcome message sent by the server in reply to the initial
   connection.  (This message sometimes contains disclaimers or help information
   that may be relevant to the user.)


.. method:: FTP.login(user='anonymous', passwd='', acct='')

   Log in as the given *user*.  The *passwd* and *acct* parameters are optional and
   default to the empty string.  If no *user* is specified, it defaults to
   ``'anonymous'``.  If *user* is ``'anonymous'``, the default *passwd* is
   ``'anonymous@'``.  This function should be called only once for each instance,
   after a connection has been established; it should not be called at all if a
   host and user were given when the instance was created.  Most FTP commands are
   only allowed after the client has logged in.  The *acct* parameter supplies
   "accounting information"; few systems implement this.


.. method:: FTP.abort()

   Abort a file transfer that is in progress.  Using this does not always work, but
   it's worth a try.


.. method:: FTP.sendcmd(cmd)

   Send a simple command string to the server and return the response string.

   .. audit-event:: ftplib.sendcmd self,cmd ftplib.FTP.sendcmd


.. method:: FTP.voidcmd(cmd)

   Send a simple command string to the server and handle the response.  Return
   nothing if a response code corresponding to success (codes in the range
   200--299) is received.  Raise :exc:`error_reply` otherwise.

   .. audit-event:: ftplib.sendcmd self,cmd ftplib.FTP.voidcmd


.. method:: FTP.retrbinary(cmd, callback, blocksize=8192, rest=None)

   Retrieve a file in binary transfer mode.  *cmd* should be an appropriate
   ``RETR`` command: ``'RETR filename'``. The *callback* function is called for
   each block of data received, with a single bytes argument giving the data
   block. The optional *blocksize* argument specifies the maximum chunk size to
   read on the low-level socket object created to do the actual transfer (which
   will also be the largest size of the data blocks passed to *callback*).  A
   reasonable default is chosen. *rest* means the same thing as in the
   :meth:`transfercmd` method.


.. method:: FTP.retrlines(cmd, callback=None)

   Retrieve a file or directory listing in the encoding specified by the
   *encoding* parameter at initialization.
   *cmd* should be an appropriate ``RETR`` command (see :meth:`retrbinary`) or
   a command such as ``LIST`` or ``NLST`` (usually just the string ``'LIST'``).
   ``LIST`` retrieves a list of files and information about those files.
   ``NLST`` retrieves a list of file names.
   The *callback* function is called for each line with a string argument
   containing the line with the trailing CRLF stripped.  The default *callback*
   prints the line to ``sys.stdout``.


.. method:: FTP.set_pasv(val)

   Enable "passive" mode if *val* is true, otherwise disable passive mode.
   Passive mode is on by default.


.. method:: FTP.storbinary(cmd, fp, blocksize=8192, callback=None, rest=None)

   Store a file in binary transfer mode.  *cmd* should be an appropriate
   ``STOR`` command: ``"STOR filename"``. *fp* is a :term:`file object`
   (opened in binary mode) which is read until EOF using its :meth:`~io.IOBase.read`
   method in blocks of size *blocksize* to provide the data to be stored.
   The *blocksize* argument defaults to 8192.  *callback* is an optional single
   parameter callable that is called on each block of data after it is sent.
   *rest* means the same thing as in the :meth:`transfercmd` method.

   .. versionchanged:: 3.2
      *rest* parameter added.


.. method:: FTP.storlines(cmd, fp, callback=None)

   Store a file in line mode.  *cmd* should be an appropriate
   ``STOR`` command (see :meth:`storbinary`).  Lines are read until EOF from the
   :term:`file object` *fp* (opened in binary mode) using its :meth:`~io.IOBase.readline`
   method to provide the data to be stored.  *callback* is an optional single
   parameter callable that is called on each line after it is sent.


.. method:: FTP.transfercmd(cmd, rest=None)

   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 an ``EPSV`` or ``PASV``
   command, connect to it, and start the transfer command.  Either way, return the
   socket for the connection.

   If optional *rest* is given, a ``REST`` command is sent to the server, passing
   *rest* as an argument.  *rest* is usually a byte offset into the requested file,
   telling the server to restart sending the file's bytes at the requested offset,
   skipping over the initial bytes.  Note however that the :meth:`transfercmd`
   method converts *rest* to a string with the *encoding* parameter specified
   at initialization, but no check is performed on the string's contents.  If the
   server does not recognize the ``REST`` command, an :exc:`error_reply` exception
   will be raised.  If this happens, simply call :meth:`transfercmd` without a
   *rest* argument.


.. method:: FTP.ntransfercmd(cmd, rest=None)

   Like :meth:`transfercmd`, but returns a tuple of the data connection and the
   expected size of the data.  If the expected size could not be computed, ``None``
   will be returned as the expected size.  *cmd* and *rest* means the same thing as
   in :meth:`transfercmd`.


.. method:: FTP.mlsd(path="", facts=[])

   List a directory in a standardized format by using ``MLSD`` command
   (:rfc:`3659`).  If *path* is omitted the current directory is assumed.
   *facts* is a list of strings representing the type of information desired
   (e.g. ``["type", "size", "perm"]``).  Return a generator object yielding a
   tuple of two elements for every file found in path.  First element is the
   file name, the second one is a dictionary containing facts about the file
   name.  Content of this dictionary might be limited by the *facts* argument
   but server is not guaranteed to return all requested facts.

   .. versionadded:: 3.3


.. method:: FTP.nlst(argument[, ...])

   Return a list of file names as returned by the ``NLST`` command.  The
   optional *argument* is a directory to list (default is the current server
   directory).  Multiple arguments can be used to pass non-standard options to
   the ``NLST`` command.

   .. note:: If your server supports the command, :meth:`mlsd` offers a better API.


.. method:: FTP.dir(argument[, ...])

   Produce a directory listing as returned by the ``LIST`` command, printing it to
   standard output.  The optional *argument* is a directory to list (default is the
   current server directory).  Multiple arguments can be used to pass non-standard
   options to the ``LIST`` command.  If the last argument is a function, it is used
   as a *callback* function as for :meth:`retrlines`; the default prints to
   ``sys.stdout``.  This method returns ``None``.

   .. note:: If your server supports the command, :meth:`mlsd` offers a better API.


.. method:: FTP.rename(fromname, toname)

   Rename file *fromname* on the server to *toname*.


.. method:: FTP.delete(filename)

   Remove the file named *filename* from the server.  If successful, returns the
   text of the response, otherwise raises :exc:`error_perm` on permission errors or
   :exc:`error_reply` on other errors.


.. method:: FTP.cwd(pathname)

   Set the current directory on the server.


.. method:: FTP.mkd(pathname)

   Create a new directory on the server.


.. method:: FTP.pwd()

   Return the pathname of the current directory on the server.


.. method:: FTP.rmd(dirname)

   Remove the directory named *dirname* on the server.


.. method:: FTP.size(filename)

   Request the size of the file named *filename* on the server.  On success, the
   size of the file is returned as an integer, otherwise ``None`` is returned.
   Note that the ``SIZE`` command is not  standardized, but is supported by many
   common server implementations.


.. method:: FTP.quit()

   Send a ``QUIT`` command to the server and close the connection. This is the
   "polite" way to close a connection, but it may raise an exception if the server
   responds with an error to the ``QUIT`` command.  This implies a call to the
   :meth:`close` method which renders the :class:`FTP` instance useless for
   subsequent calls (see below).


.. method:: FTP.close()

   Close the connection unilaterally.  This should not be applied to an already
   closed connection such as after a successful call to :meth:`~FTP.quit`.
   After this call the :class:`FTP` instance should not be used any more (after
   a call to :meth:`close` or :meth:`~FTP.quit` you cannot reopen the
   connection by issuing another :meth:`login` method).


FTP_TLS Objects
---------------

:class:`FTP_TLS` class inherits from :class:`FTP`, defining these additional objects:

.. attribute:: FTP_TLS.ssl_version

   The SSL version to use (defaults to :attr:`ssl.PROTOCOL_SSLv23`).

.. method:: FTP_TLS.auth()

   Set up a secure control connection by using TLS or SSL, depending on what
   is specified in the :attr:`ssl_version` attribute.

   .. versionchanged:: 3.4
      The method now supports hostname check with
      :attr:`ssl.SSLContext.check_hostname` and *Server Name Indication* (see
      :data:`ssl.HAS_SNI`).

.. method:: FTP_TLS.ccc()

   Revert control channel back to plaintext.  This can be useful to take
   advantage of firewalls that know how to handle NAT with non-secure FTP
   without opening fixed ports.

   .. versionadded:: 3.3

.. method:: FTP_TLS.prot_p()

   Set up secure data connection.

.. method:: FTP_TLS.prot_c()

   Set up clear text data connection.