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-\section{\module{tokenize} ---
- Tokenizer for Python source}
-
-\declaremodule{standard}{tokenize}
-\modulesynopsis{Lexical scanner for Python source code.}
-\moduleauthor{Ka Ping Yee}{}
-\sectionauthor{Fred L. Drake, Jr.}{fdrake@acm.org}
-
-
-The \module{tokenize} module provides a lexical scanner for Python
-source code, implemented in Python. The scanner in this module
-returns comments as tokens as well, making it useful for implementing
-``pretty-printers,'' including colorizers for on-screen displays.
-
-The primary entry point is a generator:
-
-\begin{funcdesc}{generate_tokens}{readline}
- The \function{generate_tokens()} generator requires one argment,
- \var{readline}, which must be a callable object which
- provides the same interface as the \method{readline()} method of
- built-in file objects (see section~\ref{bltin-file-objects}). Each
- call to the function should return one line of input as a string.
-
- The generator produces 5-tuples with these members:
- the token type;
- the token string;
- a 2-tuple \code{(\var{srow}, \var{scol})} of ints specifying the
- row and column where the token begins in the source;
- a 2-tuple \code{(\var{erow}, \var{ecol})} of ints specifying the
- row and column where the token ends in the source;
- and the line on which the token was found.
- The line passed is the \emph{logical} line;
- continuation lines are included.
- \versionadded{2.2}
-\end{funcdesc}
-
-An older entry point is retained for backward compatibility:
-
-\begin{funcdesc}{tokenize}{readline\optional{, tokeneater}}
- The \function{tokenize()} function accepts two parameters: one
- representing the input stream, and one providing an output mechanism
- for \function{tokenize()}.
-
- The first parameter, \var{readline}, must be a callable object which
- provides the same interface as the \method{readline()} method of
- built-in file objects (see section~\ref{bltin-file-objects}). Each
- call to the function should return one line of input as a string.
- Alternately, \var{readline} may be a callable object that signals
- completion by raising \exception{StopIteration}.
- \versionchanged[Added \exception{StopIteration} support]{2.5}
-
- The second parameter, \var{tokeneater}, must also be a callable
- object. It is called once for each token, with five arguments,
- corresponding to the tuples generated by \function{generate_tokens()}.
-\end{funcdesc}
-
-
-All constants from the \refmodule{token} module are also exported from
-\module{tokenize}, as are two additional token type values that might be
-passed to the \var{tokeneater} function by \function{tokenize()}:
-
-\begin{datadesc}{COMMENT}
- Token value used to indicate a comment.
-\end{datadesc}
-\begin{datadesc}{NL}
- Token value used to indicate a non-terminating newline. The NEWLINE
- token indicates the end of a logical line of Python code; NL tokens
- are generated when a logical line of code is continued over multiple
- physical lines.
-\end{datadesc}
-
-Another function is provided to reverse the tokenization process.
-This is useful for creating tools that tokenize a script, modify
-the token stream, and write back the modified script.
-
-\begin{funcdesc}{untokenize}{iterable}
- Converts tokens back into Python source code. The \var{iterable}
- must return sequences with at least two elements, the token type and
- the token string. Any additional sequence elements are ignored.
-
- The reconstructed script is returned as a single string. The
- result is guaranteed to tokenize back to match the input so that
- the conversion is lossless and round-trips are assured. The
- guarantee applies only to the token type and token string as
- the spacing between tokens (column positions) may change.
- \versionadded{2.5}
-\end{funcdesc}
-
-Example of a script re-writer that transforms float literals into
-Decimal objects:
-\begin{verbatim}
-def decistmt(s):
- """Substitute Decimals for floats in a string of statements.
-
- >>> from decimal import Decimal
- >>> s = 'print +21.3e-5*-.1234/81.7'
- >>> decistmt(s)
- "print +Decimal ('21.3e-5')*-Decimal ('.1234')/Decimal ('81.7')"
-
- >>> exec(s)
- -3.21716034272e-007
- >>> exec(decistmt(s))
- -3.217160342717258261933904529E-7
-
- """
- result = []
- g = generate_tokens(StringIO(s).readline) # tokenize the string
- for toknum, tokval, _, _, _ in g:
- if toknum == NUMBER and '.' in tokval: # replace NUMBER tokens
- result.extend([
- (NAME, 'Decimal'),
- (OP, '('),
- (STRING, repr(tokval)),
- (OP, ')')
- ])
- else:
- result.append((toknum, tokval))
- return untokenize(result)
-\end{verbatim}