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Another try at clarifying what goes into and comes out of Unicode objects.

This commit is contained in:
Fred Drake 2002-09-24 21:08:37 +00:00
parent d8ce87ad84
commit 3e930ba55f
2 changed files with 46 additions and 31 deletions
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4
Doc/lib/libfuncs.tex
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@ -568,10 +568,6 @@ def my_import(name):
\begin{funcdesc}{len}{s}
Return the length (the number of items) of an object. The argument
may be a sequence (string, tuple or list) or a mapping (dictionary).
In the case of Unicode strings, \function{len()} returns the number
of storage units, not abstract characters. In particular, when a
surrogate pair is encountered, each component of the pair is counted
as a separate character.
\end{funcdesc}
\begin{funcdesc}{list}{\optional{sequence}}

73
Doc/ref/ref2.tex
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@ -410,29 +410,48 @@ to those used by Standard C. The recognized escape sequences are:
\index{Standard C}
\index{C}
\begin{tableii}{l|l}{code}{Escape Sequence}{Meaning}
\lineii{\e\var{newline}} {Ignored}
\lineii{\e\e} {Backslash (\code{\e})}
\lineii{\e'} {Single quote (\code{'})}
\lineii{\e"} {Double quote (\code{"})}
\lineii{\e a} {\ASCII{} Bell (BEL)}
\lineii{\e b} {\ASCII{} Backspace (BS)}
\lineii{\e f} {\ASCII{} Formfeed (FF)}
\lineii{\e n} {\ASCII{} Linefeed (LF)}
\lineii{\e N\{\var{name}\}}
{Character named \var{name} in the Unicode database (Unicode only)}
\lineii{\e r} {\ASCII{} Carriage Return (CR)}
\lineii{\e t} {\ASCII{} Horizontal Tab (TAB)}
\lineii{\e u\var{xxxx}} {Character with 16-bit hex value \var{xxxx} (Unicode only)}
\lineii{\e U\var{xxxxxxxx}}{Character with 32-bit hex value \var{xxxxxxxx} (Unicode only)}
\lineii{\e v} {\ASCII{} Vertical Tab (VT)}
\lineii{\e\var{ooo}} {\ASCII{} character with octal value \var{ooo}}
\lineii{\e x\var{hh}} {\ASCII{} character with hex value \var{hh}}
\end{tableii}
\begin{tableiii}{l|l|c}{code}{Escape Sequence}{Meaning}{Notes}
\lineiii{\e\var{newline}} {Ignored}{}
\lineiii{\e\e} {Backslash (\code{\e})}{}
\lineiii{\e'} {Single quote (\code{'})}{}
\lineiii{\e"} {Double quote (\code{"})}{}
\lineiii{\e a} {\ASCII{} Bell (BEL)}{}
\lineiii{\e b} {\ASCII{} Backspace (BS)}{}
\lineiii{\e f} {\ASCII{} Formfeed (FF)}{}
\lineiii{\e n} {\ASCII{} Linefeed (LF)}{}
\lineiii{\e N\{\var{name}\}}
{Character named \var{name} in the Unicode database (Unicode only)}{}
\lineiii{\e r} {\ASCII{} Carriage Return (CR)}{}
\lineiii{\e t} {\ASCII{} Horizontal Tab (TAB)}{}
\lineiii{\e u\var{xxxx}}
{Character with 16-bit hex value \var{xxxx} (Unicode only)}{(1)}
\lineiii{\e U\var{xxxxxxxx}}
{Character with 32-bit hex value \var{xxxxxxxx} (Unicode only)}{(2)}
\lineiii{\e v} {\ASCII{} Vertical Tab (VT)}{}
\lineiii{\e\var{ooo}} {\ASCII{} character with octal value \var{ooo}}{(3)}
\lineiii{\e x\var{hh}} {\ASCII{} character with hex value \var{hh}}{(4)}
\end{tableiii}
\index{ASCII@\ASCII}
As in Standard C, up to three octal digits are accepted. However,
exactly two hex digits are taken in hex escapes.
\noindent
Notes:
\begin{itemize}
\item[(1)]
Individual code units which form parts of a surrogate pair can be
encoded using this escape sequence.
\item[(2)]
Any Unicode character can be encoded this way, but characters
outside the Basic Multilingual Plane (BMP) will be encoded using a
surrogate pair if Python is compiled to use 16-bit code units (the
default). Individual code units which form parts of a surrogate
pair can be encoded using this escape sequence.
\item[(3)]
As in Standard C, up to three octal digits are accepted.
\item[(4)]
Unlike in Standard C, at most two hex digits are accepted.
\end{itemize}
Unlike Standard \index{unrecognized escape sequence}C,
all unrecognized escape sequences are left in the string unchanged,
@ -460,12 +479,12 @@ as part of the string, \emph{not} as a line continuation.
When an \character{r} or \character{R} prefix is used in conjunction
with a \character{u} or \character{U} prefix, then the \code{\e uXXXX}
escape sequence is processed while \emph{all other backslashes are
left in the string}. For example, the string literal \code{ur"\e
u0062\e n"} consists of three Unicode characters: `LATIN SMALL LETTER
B', `REVERSE SOLIDUS', and `LATIN SMALL LETTER N'. Backslashes can be
escaped with a preceding backslash; however, both remain in the
string. As a result, \code{\e uXXXX} escape sequences are only
recognized when there are an odd number of backslashes.
left in the string}. For example, the string literal
\code{ur"\e{}u0062\e n"} consists of three Unicode characters: `LATIN
SMALL LETTER B', `REVERSE SOLIDUS', and `LATIN SMALL LETTER N'.
Backslashes can be escaped with a preceding backslash; however, both
remain in the string. As a result, \code{\e uXXXX} escape sequences
are only recognized when there are an odd number of backslashes.
\subsection{String literal concatenation\label{string-catenation}}