mirror of https://github.com/python/cpython.git
133 lines
5.1 KiB
TeX
133 lines
5.1 KiB
TeX
\section{Standard Module \sectcode{urllib}}
|
|
\label{module-urllib}
|
|
\stmodindex{urllib}
|
|
\index{WWW}
|
|
\index{World-Wide Web}
|
|
\index{URL}
|
|
|
|
|
|
This module provides a high-level interface for fetching data across
|
|
the World-Wide Web. In particular, the \function{urlopen()} function
|
|
is similar to the built-in function \function{open()}, but accepts
|
|
Universal Resource Locators (URLs) instead of filenames. Some
|
|
restrictions apply --- it can only open URLs for reading, and no seek
|
|
operations are available.
|
|
|
|
It defines the following public functions:
|
|
|
|
\begin{funcdesc}{urlopen}{url}
|
|
Open a network object denoted by a URL for reading. If the URL does
|
|
not have a scheme identifier, or if it has \file{file:} as its scheme
|
|
identifier, this opens a local file; otherwise it opens a socket to a
|
|
server somewhere on the network. If the connection cannot be made, or
|
|
if the server returns an error code, the \exception{IOError} exception
|
|
is raised. If all went well, a file-like object is returned. This
|
|
supports the following methods: \method{read()}, \method{readline()},
|
|
\method{readlines()}, \method{fileno()}, \method{close()} and
|
|
\method{info()}.
|
|
Except for the last one, these methods have the same interface as for
|
|
file objects --- see section \ref{bltin-file-objects} in this
|
|
manual. (It is not a built-in file object, however, so it can't be
|
|
used at those few places where a true built-in file object is
|
|
required.)
|
|
|
|
The \method{info()} method returns an instance of the class
|
|
\class{mimetools.Message} containing the headers received from the
|
|
server, if the protocol uses such headers (currently the only
|
|
supported protocol that uses this is HTTP). See the description of
|
|
the \module{mimetools}\refstmodindex{mimetools} module.
|
|
\end{funcdesc}
|
|
|
|
\begin{funcdesc}{urlretrieve}{url}
|
|
Copy a network object denoted by a URL to a local file, if necessary.
|
|
If the URL points to a local file, or a valid cached copy of the
|
|
object exists, the object is not copied. Return a tuple
|
|
\code{(\var{filename}, \var{headers})} where \var{filename} is the
|
|
local file name under which the object can be found, and \var{headers}
|
|
is either \code{None} (for a local object) or whatever the
|
|
\method{info()} method of the object returned by \function{urlopen()}
|
|
returned (for a remote object, possibly cached). Exceptions are the
|
|
same as for \function{urlopen()}.
|
|
\end{funcdesc}
|
|
|
|
\begin{funcdesc}{urlcleanup}{}
|
|
Clear the cache that may have been built up by previous calls to
|
|
\function{urlretrieve()}.
|
|
\end{funcdesc}
|
|
|
|
\begin{funcdesc}{quote}{string\optional{\, addsafe}}
|
|
Replace special characters in \var{string} using the \samp{\%xx} escape.
|
|
Letters, digits, and the characters \character{_,.-} are never quoted.
|
|
The optional \var{addsafe} parameter specifies additional characters
|
|
that should not be quoted --- its default value is \code{'/'}.
|
|
|
|
Example: \code{quote('/\~connolly/')} yields \code{'/\%7econnolly/'}.
|
|
\end{funcdesc}
|
|
|
|
\begin{funcdesc}{quote_plus}{string\optional{\, addsafe}}
|
|
Like \function{quote()}, but also replaces spaces by plus signs, as
|
|
required for quoting HTML form values.
|
|
\end{funcdesc}
|
|
|
|
\begin{funcdesc}{unquote}{string}
|
|
Replace \samp{\%xx} escapes by their single-character equivalent.
|
|
|
|
Example: \code{unquote('/\%7Econnolly/')} yields \code{'/\~connolly/'}.
|
|
\end{funcdesc}
|
|
|
|
\begin{funcdesc}{unquote_plus}{string}
|
|
Like \function{unquote()}, but also replaces plus signs by spaces, as
|
|
required for unquoting HTML form values.
|
|
\end{funcdesc}
|
|
|
|
Restrictions:
|
|
|
|
\begin{itemize}
|
|
|
|
\item
|
|
Currently, only the following protocols are supported: HTTP, (versions
|
|
0.9 and 1.0), Gopher (but not Gopher-+), FTP, and local files.
|
|
\indexii{HTTP}{protocol}
|
|
\indexii{Gopher}{protocol}
|
|
\indexii{FTP}{protocol}
|
|
|
|
\item
|
|
The caching feature of \function{urlretrieve()} has been disabled
|
|
until I find the time to hack proper processing of Expiration time
|
|
headers.
|
|
|
|
\item
|
|
There should be a function to query whether a particular URL is in
|
|
the cache.
|
|
|
|
\item
|
|
For backward compatibility, if a URL appears to point to a local file
|
|
but the file can't be opened, the URL is re-interpreted using the FTP
|
|
protocol. This can sometimes cause confusing error messages.
|
|
|
|
\item
|
|
The \function{urlopen()} and \function{urlretrieve()} functions can
|
|
cause arbitrarily long delays while waiting for a network connection
|
|
to be set up. This means that it is difficult to build an interactive
|
|
web client using these functions without using threads.
|
|
|
|
\item
|
|
The data returned by \function{urlopen()} or \function{urlretrieve()}
|
|
is the raw data returned by the server. This may be binary data
|
|
(e.g. an image), plain text or (for example) HTML. The HTTP protocol
|
|
provides type information in the reply header, which can be inspected
|
|
by looking at the \code{content-type} header. For the Gopher protocol,
|
|
type information is encoded in the URL; there is currently no easy way
|
|
to extract it. If the returned data is HTML, you can use the module
|
|
\module{htmllib}\refstmodindex{htmllib} to parse it.
|
|
\index{HTML}
|
|
\indexii{HTTP}{protocol}
|
|
\indexii{Gopher}{protocol}
|
|
|
|
\item
|
|
Although the \module{urllib} module contains (undocumented) routines
|
|
to parse and unparse URL strings, the recommended interface for URL
|
|
manipulation is in module \module{urlparse}\refstmodindex{urlparse}.
|
|
|
|
\end{itemize}
|