289 lines
9.8 KiB
ReStructuredText
289 lines
9.8 KiB
ReStructuredText
: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>
|
|
|
|
**Source code:** :source:`Lib/tokenize.py`
|
|
|
|
--------------
|
|
|
|
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.
|
|
|
|
To simplify token stream handling, all :ref:`operator <operators>` and
|
|
:ref:`delimiter <delimiters>` tokens and :data:`Ellipsis` are returned using
|
|
the generic :data:`~token.OP` token type. The exact
|
|
type can be determined by checking the ``exact_type`` property on the
|
|
:term:`named tuple` returned from :func:`tokenize.tokenize`.
|
|
|
|
Tokenizing Input
|
|
----------------
|
|
|
|
The primary entry point is a :term:`generator`:
|
|
|
|
.. function:: tokenize(readline)
|
|
|
|
The :func:`.tokenize` generator requires one argument, *readline*, which
|
|
must be a callable object which provides the same interface as the
|
|
:meth:`io.IOBase.readline` method of file objects. Each call to the
|
|
function should return one line of input as bytes.
|
|
|
|
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 (the last tuple item)
|
|
is the *logical* line; continuation lines are included. The 5 tuple is
|
|
returned as a :term:`named tuple` with the field names:
|
|
``type string start end line``.
|
|
|
|
The returned :term:`named tuple` has an additional property named
|
|
``exact_type`` that contains the exact operator type for
|
|
:data:`~token.OP` tokens. For all other token types ``exact_type``
|
|
equals the named tuple ``type`` field.
|
|
|
|
.. versionchanged:: 3.1
|
|
Added support for named tuples.
|
|
|
|
.. versionchanged:: 3.3
|
|
Added support for ``exact_type``.
|
|
|
|
:func:`.tokenize` determines the source encoding of the file by looking for a
|
|
UTF-8 BOM or encoding cookie, according to :pep:`263`.
|
|
|
|
|
|
All constants from the :mod:`token` module are also exported from
|
|
:mod:`tokenize`.
|
|
|
|
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.
|
|
|
|
It returns bytes, encoded using the :data:`~token.ENCODING` token, which
|
|
is the first token sequence output by :func:`.tokenize`.
|
|
|
|
|
|
:func:`.tokenize` needs to detect the encoding of source files it tokenizes. The
|
|
function it uses to do this is available:
|
|
|
|
.. function:: detect_encoding(readline)
|
|
|
|
The :func:`detect_encoding` function is used to detect the encoding that
|
|
should be used to decode a Python source file. It requires one argument,
|
|
readline, in the same way as the :func:`.tokenize` generator.
|
|
|
|
It will call readline a maximum of twice, and return the encoding used
|
|
(as a string) and a list of any lines (not decoded from bytes) it has read
|
|
in.
|
|
|
|
It detects the encoding from the presence of a UTF-8 BOM or an encoding
|
|
cookie as specified in :pep:`263`. If both a BOM and a cookie are present,
|
|
but disagree, a :exc:`SyntaxError` will be raised. Note that if the BOM is found,
|
|
``'utf-8-sig'`` will be returned as an encoding.
|
|
|
|
If no encoding is specified, then the default of ``'utf-8'`` will be
|
|
returned.
|
|
|
|
Use :func:`.open` to open Python source files: it uses
|
|
:func:`detect_encoding` to detect the file encoding.
|
|
|
|
|
|
.. function:: open(filename)
|
|
|
|
Open a file in read only mode using the encoding detected by
|
|
:func:`detect_encoding`.
|
|
|
|
.. versionadded:: 3.2
|
|
|
|
.. exception:: TokenError
|
|
|
|
Raised when either a docstring or expression that may be split over several
|
|
lines is not completed anywhere in the file, for example::
|
|
|
|
"""Beginning of
|
|
docstring
|
|
|
|
or::
|
|
|
|
[1,
|
|
2,
|
|
3
|
|
|
|
Note that unclosed single-quoted strings do not cause an error to be
|
|
raised. They are tokenized as :data:`~token.ERRORTOKEN`, followed by the
|
|
tokenization of their contents.
|
|
|
|
|
|
.. _tokenize-cli:
|
|
|
|
Command-Line Usage
|
|
------------------
|
|
|
|
.. versionadded:: 3.3
|
|
|
|
The :mod:`tokenize` module can be executed as a script from the command line.
|
|
It is as simple as:
|
|
|
|
.. code-block:: sh
|
|
|
|
python -m tokenize [-e] [filename.py]
|
|
|
|
The following options are accepted:
|
|
|
|
.. program:: tokenize
|
|
|
|
.. cmdoption:: -h, --help
|
|
|
|
show this help message and exit
|
|
|
|
.. cmdoption:: -e, --exact
|
|
|
|
display token names using the exact type
|
|
|
|
If :file:`filename.py` is specified its contents are tokenized to stdout.
|
|
Otherwise, tokenization is performed on stdin.
|
|
|
|
Examples
|
|
------------------
|
|
|
|
Example of a script rewriter that transforms float literals into Decimal
|
|
objects::
|
|
|
|
from tokenize import tokenize, untokenize, NUMBER, STRING, NAME, OP
|
|
from io import BytesIO
|
|
|
|
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'))"
|
|
|
|
The format of the exponent is inherited from the platform C library.
|
|
Known cases are "e-007" (Windows) and "e-07" (not Windows). Since
|
|
we're only showing 12 digits, and the 13th isn't close to 5, the
|
|
rest of the output should be platform-independent.
|
|
|
|
>>> exec(s) #doctest: +ELLIPSIS
|
|
-3.21716034272e-0...7
|
|
|
|
Output from calculations with Decimal should be identical across all
|
|
platforms.
|
|
|
|
>>> exec(decistmt(s))
|
|
-3.217160342717258261933904529E-7
|
|
"""
|
|
result = []
|
|
g = tokenize(BytesIO(s.encode('utf-8')).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).decode('utf-8')
|
|
|
|
Example of tokenizing from the command line. The script::
|
|
|
|
def say_hello():
|
|
print("Hello, World!")
|
|
|
|
say_hello()
|
|
|
|
will be tokenized to the following output where the first column is the range
|
|
of the line/column coordinates where the token is found, the second column is
|
|
the name of the token, and the final column is the value of the token (if any)
|
|
|
|
.. code-block:: shell-session
|
|
|
|
$ python -m tokenize hello.py
|
|
0,0-0,0: ENCODING 'utf-8'
|
|
1,0-1,3: NAME 'def'
|
|
1,4-1,13: NAME 'say_hello'
|
|
1,13-1,14: OP '('
|
|
1,14-1,15: OP ')'
|
|
1,15-1,16: OP ':'
|
|
1,16-1,17: NEWLINE '\n'
|
|
2,0-2,4: INDENT ' '
|
|
2,4-2,9: NAME 'print'
|
|
2,9-2,10: OP '('
|
|
2,10-2,25: STRING '"Hello, World!"'
|
|
2,25-2,26: OP ')'
|
|
2,26-2,27: NEWLINE '\n'
|
|
3,0-3,1: NL '\n'
|
|
4,0-4,0: DEDENT ''
|
|
4,0-4,9: NAME 'say_hello'
|
|
4,9-4,10: OP '('
|
|
4,10-4,11: OP ')'
|
|
4,11-4,12: NEWLINE '\n'
|
|
5,0-5,0: ENDMARKER ''
|
|
|
|
The exact token type names can be displayed using the :option:`-e` option:
|
|
|
|
.. code-block:: shell-session
|
|
|
|
$ python -m tokenize -e hello.py
|
|
0,0-0,0: ENCODING 'utf-8'
|
|
1,0-1,3: NAME 'def'
|
|
1,4-1,13: NAME 'say_hello'
|
|
1,13-1,14: LPAR '('
|
|
1,14-1,15: RPAR ')'
|
|
1,15-1,16: COLON ':'
|
|
1,16-1,17: NEWLINE '\n'
|
|
2,0-2,4: INDENT ' '
|
|
2,4-2,9: NAME 'print'
|
|
2,9-2,10: LPAR '('
|
|
2,10-2,25: STRING '"Hello, World!"'
|
|
2,25-2,26: RPAR ')'
|
|
2,26-2,27: NEWLINE '\n'
|
|
3,0-3,1: NL '\n'
|
|
4,0-4,0: DEDENT ''
|
|
4,0-4,9: NAME 'say_hello'
|
|
4,9-4,10: LPAR '('
|
|
4,10-4,11: RPAR ')'
|
|
4,11-4,12: NEWLINE '\n'
|
|
5,0-5,0: ENDMARKER ''
|
|
|
|
Example of tokenizing a file programmatically, reading unicode
|
|
strings instead of bytes with :func:`generate_tokens`::
|
|
|
|
import tokenize
|
|
|
|
with tokenize.open('hello.py') as f:
|
|
tokens = tokenize.generate_tokens(f.readline)
|
|
for token in tokens:
|
|
print(token)
|
|
|
|
Or reading bytes directly with :func:`.tokenize`::
|
|
|
|
import tokenize
|
|
|
|
with open('hello.py', 'rb') as f:
|
|
tokens = tokenize.tokenize(f.readline)
|
|
for token in tokens:
|
|
print(token)
|