Doc/library/ftplib.rst

:mod:`ftplib` --- FTP protocol client
=====================================

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


.. 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`.

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

   >>> from ftplib import FTP
   >>> ftp = FTP('ftp.cwi.nl')   # connect to host, default port
   >>> ftp.login()               # user anonymous, passwd anonymous@
   >>> ftp.retrlines('LIST')     # list directory contents
   total 24418
   drwxrwsr-x   5 ftp-usr  pdmaint     1536 Mar 20 09:48 .
   dr-xr-srwt 105 ftp-usr  pdmaint     1536 Mar 21 14:32 ..
   -rw-r--r--   1 ftp-usr  pdmaint     5305 Mar 20 09:48 INDEX
    .
    .
    .
   >>> ftp.retrbinary('RETR README', open('README', 'wb').write)
   '226 Transfer complete.'
   >>> ftp.quit()

The module defines the following items:


.. class:: FTP(host='', user='', passwd='', acct=''[, timeout])

   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).


.. 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:`socket.error` and
   :exc:`IOError`.


.. 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.

   .. index:: single: ftpmirror.py

   The file :file:`Tools/scripts/ftpmirror.py` in the Python source distribution is
   a script that can mirror FTP sites, or portions thereof, using the :mod:`ftplib`
   module. It can be used as an extended example that applies this module.


.. _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])

   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.


.. 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.


.. 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.


.. 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 string 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 ASCII transfer mode.  *cmd* should be
   an appropriate ``RETR`` command (see :meth:`retrbinary`) or a command such as
   ``LIST``, ``NLST`` or ``MLSD`` (usually just the string ``'LIST'``).
   ``LIST`` retrieves a list of files and information about those files.
   ``NLST`` retrieves a list of file names.  On some servers, ``MLSD`` retrieves
   a machine readable list of files and information about those files.  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(boolean)

   Enable "passive" mode if *boolean* is true, other disable passive mode.
   Passive mode is on by default.


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

   Store a file in binary transfer mode.  *cmd* should be an appropriate
   ``STOR`` command: ``"STOR filename"``. *file* is an open :term:`file object`
   which is read until EOF using its :meth:`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.


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

   Store a file in ASCII transfer mode.  *cmd* should be an appropriate
   ``STOR`` command (see :meth:`storbinary`).  Lines are read until EOF from the
   open :term:`file object` *file* using its :meth:`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 a
   ``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``
   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 RFC 959 requires only that
   *rest* be a string containing characters in the printable range from ASCII code
   33 to ASCII code 126.  The :meth:`transfercmd` method, therefore, converts
   *rest* to a string, 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.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.


.. 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``.


.. 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:`quit`.  After this
   call the :class:`FTP` instance should not be used any more (after a call to
   :meth:`close` or :meth:`quit` you cannot reopen the connection by issuing
   another :meth:`login` method).