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