mirror of
https://github.com/python/cpython
synced 2024-11-02 14:48:31 +00:00
e47da0ae04
* \bcode, \ecode added everywhere
* \label{module-foo} added everywhere
* A few \seealso sections added.
* Indentation fixed inside verbatim in lib*tex files
132 lines
5 KiB
TeX
132 lines
5 KiB
TeX
\section{Standard Module \sectcode{urllib}}
|
|
\label{module-urllib}
|
|
\stmodindex{urllib}
|
|
\index{WWW}
|
|
\index{World-Wide Web}
|
|
\index{URL}
|
|
|
|
\renewcommand{\indexsubitem}{(in module urllib)}
|
|
|
|
This module provides a high-level interface for fetching data across
|
|
the World-Wide Web. In particular, the \code{urlopen} function is
|
|
similar to the built-in function \code{open}, but accepts URLs
|
|
(Universal Resource Locators) 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 \samp{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 \code{IOError} exception is
|
|
raised. If all went well, a file-like object is returned. This
|
|
supports the following methods: \code{read()}, \code{readline()},
|
|
\code{readlines()}, \code{fileno()}, \code{close()} and \code{info()}.
|
|
Except for the last one, these methods have the same interface as for
|
|
file objects --- see the section on File Objects earlier in this
|
|
manual. (It's 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 \code{info()} method returns an instance of the class
|
|
\code{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
|
|
\code{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 (\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 \code{info()} method of the object
|
|
returned by \code{urlopen()} returned (for a remote object, possibly
|
|
cached). Exceptions are the same as for \code{urlopen()}.
|
|
\end{funcdesc}
|
|
|
|
\begin{funcdesc}{urlcleanup}{}
|
|
Clear the cache that may have been built up by previous calls to
|
|
\code{urlretrieve()}.
|
|
\end{funcdesc}
|
|
|
|
\begin{funcdesc}{quote}{string\optional{\, addsafe}}
|
|
Replace special characters in \var{string} using the \code{\%xx} escape.
|
|
Letters, digits, and the characters ``\code{_,.-}'' 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 \code{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 \code{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.
|
|
\index{HTTP}
|
|
\index{Gopher}
|
|
\index{FTP}
|
|
|
|
\item
|
|
The caching feature of \code{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 \code{urlopen()} and \code{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 \code{urlopen()} or \code{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
|
|
\code{htmllib} to parse it.
|
|
\index{HTML}
|
|
\index{HTTP}
|
|
\index{Gopher}
|
|
\stmodindex{htmllib}
|
|
|
|
\item
|
|
Although the \code{urllib} module contains (undocumented) routines to
|
|
parse and unparse URL strings, the recommended interface for URL
|
|
manipulation is in module \code{urlparse}.
|
|
\stmodindex{urlparse}
|
|
|
|
\end{itemize}
|