20.8. "ftplib" — FTP protocol client
************************************

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

======================================================================

This module defines the class "FTP" and a few related items. The "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 "urllib" 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 "ftplib" module:

   >>> from ftplib import FTP
   >>> ftp = FTP('ftp.debian.org')     # connect to host, default port
   >>> ftp.login()                     # user anonymous, passwd anonymous@
   '230 Login successful.'
   >>> ftp.cwd('debian')               # change into "debian" directory
   >>> 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.'
   >>> ftp.retrbinary('RETR README', open('README', 'wb').write)
   '226 Transfer complete.'
   >>> ftp.quit()

The module defines the following items:

class ftplib.FTP([host[, user[, passwd[, acct[, timeout]]]]])

   Return a new instance of the "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).

   Changed in version 2.6: *timeout* was added.

class ftplib.FTP_TLS([host[, user[, passwd[, acct[, keyfile[, certfile[, context[, timeout]]]]]]]])

   A "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 "prot_p()" method.  *context* is a "ssl.SSLContext" object
   which allows bundling SSL configuration options, certificates and
   private keys into a single (potentially long-lived) structure.
   Please read Security considerations 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.

   New in version 2.7.

   Changed in version 2.7.10: The *context* parameter was added.

   Here’s a sample session using the "FTP_TLS" class:

   >>> from ftplib import FTP_TLS
   >>> ftps = FTP_TLS('ftp.python.org')
   >>> ftps.login()           # login anonymously before securing control channel
   >>> ftps.prot_p()          # switch to secure data connection
   >>> ftps.retrlines('LIST') # list directory content securely
   total 9
   drwxr-xr-x   8 root     wheel        1024 Jan  3  1994 .
   drwxr-xr-x   8 root     wheel        1024 Jan  3  1994 ..
   drwxr-xr-x   2 root     wheel        1024 Jan  3  1994 bin
   drwxr-xr-x   2 root     wheel        1024 Jan  3  1994 etc
   d-wxrwxr-x   2 ftp      wheel        1024 Sep  5 13:43 incoming
   drwxr-xr-x   2 root     wheel        1024 Nov 17  1993 lib
   drwxr-xr-x   6 1094     wheel        1024 Sep 13 19:07 pub
   drwxr-xr-x   3 root     wheel        1024 Jan  3  1994 usr
   -rw-r--r--   1 root     root          312 Aug  1  1994 welcome.msg
   '226 Transfer complete.'
   >>> ftps.quit()
   >>>

exception ftplib.error_reply

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

exception ftplib.error_temp

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

exception ftplib.error_perm

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

exception ftplib.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.

ftplib.all_errors

   The set of all exceptions (as a tuple) that methods of "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 "socket.error"
   and "IOError".

See also:

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

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


20.8.1. 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.

"FTP" instances have the following methods:

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.

FTP.connect(host[, port[, 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.

   Changed in version 2.6: *timeout* was added.

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.)

FTP.login([user[, 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.

FTP.abort()

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

FTP.sendcmd(command)

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

FTP.voidcmd(command)

   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 "error_reply" otherwise.

FTP.retrbinary(command, callback[, maxblocksize[, rest]])

   Retrieve a file in binary transfer mode.  *command* 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 *maxblocksize*
   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
   "transfercmd()" method.

FTP.retrlines(command[, callback])

   Retrieve a file or directory listing in ASCII transfer mode.
   *command* should be an appropriate "RETR" command (see
   "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".

FTP.set_pasv(val)

   Enable “passive” mode if *val* is true, otherwise disable passive
   mode.  (In Python 2.0 and before, passive mode was off by default;
   in Python 2.1 and later, it is on by default.)

FTP.storbinary(command, fp[, blocksize, callback, rest])

   Store a file in binary transfer mode.  *command* should be an
   appropriate "STOR" command: ""STOR filename"". *fp* is an open file
   object which is read until EOF using its "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
   "transfercmd()" method.

   Changed in version 2.1: default for *blocksize* added.

   Changed in version 2.6: *callback* parameter added.

   Changed in version 2.7: *rest* parameter added.

FTP.storlines(command, fp[, callback])

   Store a file in ASCII transfer mode.  *command* should be an
   appropriate "STOR" command (see "storbinary()").  Lines are read
   until EOF from the open file object *fp* using its "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.

   Changed in version 2.6: *callback* parameter added.

FTP.transfercmd(cmd[, rest])

   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 RFC 959 requires only that *rest*
   be a string containing characters in the printable range from ASCII
   code 33 to ASCII code 126.  The "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 "error_reply" exception will be raised.  If this
   happens, simply call "transfercmd()" without a *rest* argument.

FTP.ntransfercmd(cmd[, rest])

   Like "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 "transfercmd()".

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.

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 "retrlines()"; the default prints to
   "sys.stdout".  This method returns "None".

FTP.rename(fromname, toname)

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

FTP.delete(filename)

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

FTP.cwd(pathname)

   Set the current directory on the server.

FTP.mkd(pathname)

   Create a new directory on the server.

FTP.pwd()

   Return the pathname of the current directory on the server.

FTP.rmd(dirname)

   Remove the directory named *dirname* on the server.

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.

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 "close()" method which renders
   the "FTP" instance useless for subsequent calls (see below).

FTP.close()

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


20.8.2. FTP_TLS Objects
=======================

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

FTP_TLS.ssl_version

   The SSL version to use (defaults to "ssl.PROTOCOL_SSLv23").

FTP_TLS.auth()

   Set up secure control connection by using TLS or SSL, depending on
   what specified in "ssl_version()" attribute.

FTP_TLS.prot_p()

   Set up secure data connection.

FTP_TLS.prot_c()

   Set up clear text data connection.
