# 21.13. `ftplib` — FTP 协议客户端

源代码： 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.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 `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()

这个模块定义了以下内容：

class `ftplib.``FTP`(host='', user='', passwd='', acct='', timeout=None, source_address=None)

  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). source_address is a 2-tuple `(host, port)` for the socket to bind to as its source address before connecting.

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

      >>> from ftplib import FTP
      >>> with FTP("ftp1.at.proftpd.org") as ftp:
      ...     ftp.login()
      ...     ftp.dir()
      ...
      '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
      >>>

  在 3.2 版更改: 支持了 `with` 语句。

  在 3.3 版更改: source_address parameter was added.

class `ftplib.``FTP_TLS`(host='', user='', passwd='', acct='', keyfile=None, certfile=None, context=None, timeout=None, source_address=None)

  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.

  3.2 新版功能.

  在 3.3 版更改: source_address parameter was added.

  在 3.4 版更改: The class now supports hostname check with `ssl.SSLContext.check_hostname` and Server Name Indication (see `ssl.HAS_SNI`).

  3.6 版后已移除: keyfile and certfile are deprecated in favor of context. Please use `ssl.SSLContext.load_cert_chain()` instead, or let `ssl.create_default_context()` select the system’s trusted CA certificates for you.

  Here’s a sample session using the `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 `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 `OSError`.

参见

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.

## 21.13.1. 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=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.

  在 3.3 版更改: source_address parameter 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='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.

`FTP.``abort`()

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

`FTP.``sendcmd`(cmd)

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

`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 `error_reply` otherwise.

`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 `transfercmd()` method.

`FTP.``retrlines`(cmd, callback=None)

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

`FTP.``set_pasv`(val)

  Enable “passive” mode if val is true, otherwise disable passive mode. Passive mode is on by default.

`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 file object (opened in binary mode) 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.

  在 3.2 版更改: rest parameter added.

`FTP.``storlines`(cmd, fp, callback=None)

  Store a file in ASCII transfer mode. cmd should be an appropriate `STOR` command (see `storbinary()`). Lines are read until EOF from the file object fp (opened in binary mode) 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.

`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 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=None)

  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.``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.

  3.3 新版功能.

`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.

  注解

  If your server supports the command, `mlsd()` offers a better API.

`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`.

  注解

  If your server supports the command, `mlsd()` offers a better API.

`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).

## 21.13.2. 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 a secure control connection by using TLS or SSL, depending on what is specified in the `ssl_version` attribute.

  在 3.4 版更改: The method now supports hostname check with `ssl.SSLContext.check_hostname` and Server Name Indication (see `ssl.HAS_SNI`).

`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.

  3.3 新版功能.

`FTP_TLS.``prot_p`()

  Set up secure data connection.

`FTP_TLS.``prot_c`()

  Set up clear text data connection.