mirror of
https://github.com/python/cpython.git
synced 2025-11-04 07:31:38 +00:00
119 lines
4.6 KiB
TeX
119 lines
4.6 KiB
TeX
\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 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}
|