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author | Georg Brandl <georg@python.org> | 2007-08-15 14:28:22 (GMT) |
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committer | Georg Brandl <georg@python.org> | 2007-08-15 14:28:22 (GMT) |
commit | 116aa62bf54a39697e25f21d6cf6799f7faa1349 (patch) | |
tree | 8db5729518ed4ca88e26f1e26cc8695151ca3eb3 /Doc/library/tokenize.rst | |
parent | 739c01d47b9118d04e5722333f0e6b4d0c8bdd9e (diff) | |
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Move the 3k reST doc tree in place.
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-rw-r--r-- | Doc/library/tokenize.rst | 122 |
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diff --git a/Doc/library/tokenize.rst b/Doc/library/tokenize.rst new file mode 100644 index 0000000..61f2c4d --- /dev/null +++ b/Doc/library/tokenize.rst @@ -0,0 +1,122 @@ + +:mod:`tokenize` --- Tokenizer for Python source +=============================================== + +.. module:: tokenize + :synopsis: Lexical scanner for Python source code. +.. moduleauthor:: Ka Ping Yee +.. sectionauthor:: Fred L. Drake, Jr. <fdrake@acm.org> + + +The :mod:`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: + + +.. function:: generate_tokens(readline) + + The :func:`generate_tokens` generator requires one argment, *readline*, which + must be a callable object which provides the same interface as the + :meth:`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 ``(srow, scol)`` of ints specifying the row and column where + the token begins in the source; a 2-tuple ``(erow, 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 *logical* line; continuation lines are + included. + + .. versionadded:: 2.2 + +An older entry point is retained for backward compatibility: + + +.. function:: tokenize(readline[, tokeneater]) + + The :func:`tokenize` function accepts two parameters: one representing the input + stream, and one providing an output mechanism for :func:`tokenize`. + + The first parameter, *readline*, must be a callable object which provides the + same interface as the :meth:`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, *readline* may be a callable object that + signals completion by raising :exc:`StopIteration`. + + .. versionchanged:: 2.5 + Added :exc:`StopIteration` support. + + The second parameter, *tokeneater*, must also be a callable object. It is + called once for each token, with five arguments, corresponding to the tuples + generated by :func:`generate_tokens`. + +All constants from the :mod:`token` module are also exported from +:mod:`tokenize`, as are two additional token type values that might be passed to +the *tokeneater* function by :func:`tokenize`: + + +.. data:: COMMENT + + Token value used to indicate a comment. + + +.. data:: 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. + +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. + + +.. function:: untokenize(iterable) + + Converts tokens back into Python source code. The *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 + +Example of a script re-writer that transforms float literals into Decimal +objects:: + + 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) + |