32.7. tokenize — Pythonソースのためのトークナイザ

ソースコード: Lib/tokenize.py


tokenize モジュールでは、Python で実装された Python ソースコードの字句解析器を提供します。さらに、このモジュールの字句解析器はコメントもトークンとして返します。このため、このモジュールはスクリーン上で表示する際の色付け機能 (colorizers) を含む 「清書出力器 (pretty-printer)」 を実装する上で便利です。

To simplify token stream handling, all operator and delimiter tokens and Ellipsis are returned using the generic OP token type. The exact type can be determined by checking the exact_type property on the named tuple returned from tokenize.tokenize().

32.7.1. Tokenizing Input

第一のエントリポイントはジェネレータ(generator)です:

tokenize.tokenize(readline)

The tokenize() generator requires one argument, readline, which must be a callable object which provides the same interface as the 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 named tuple with the field names: type string start end line.

The returned named tuple has an additional property named exact_type that contains the exact operator type for token.OP tokens. For all other token types exact_type equals the named tuple type field.

バージョン 3.1 で変更: Added support for named tuples.

バージョン 3.3 で変更: Added support for exact_type.

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 token module are also exported from tokenize, as are three additional token type values:

tokenize.COMMENT

コメントであることを表すために使われるトークン値です。

tokenize.NL

終わりではない改行を表すために使われるトークン値。NEWLINE トークンは Pythonコードの論理行の終わりを表します。NLトークンはコードの論理行が複数の物理行にわたって続いているときに作られます。

tokenize.ENCODING

Token value that indicates the encoding used to decode the source bytes into text. The first token returned by tokenize() will always be an ENCODING token.

もう一つの関数がトークン化プロセスを逆転するために提供されています。これは、スクリプトを字句解析し、トークンのストリームに変更を加え、変更されたスクリプトを書き戻すようなツールを作成する際に便利です。

tokenize.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.

再構築されたスクリプトは一つの文字列として返されます。得られる結果はもう一度字句解析すると入力と一致することが保証されるので、変換がロスレスでありラウンドトリップできることは間違いありません。この保証はトークン型およびトークン文字列に対してのものでトークン間のスペース (コラム位置)のようなものは変わることがあり得ます。

It returns bytes, encoded using the ENCODING token, which is the first token sequence output by tokenize().

tokenize() needs to detect the encoding of source files it tokenizes. The function it uses to do this is available:

tokenize.detect_encoding(readline)

The 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 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 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 open() to open Python source files: it uses detect_encoding() to detect the file encoding.

tokenize.open(filename)

Open a file in read only mode using the encoding detected by detect_encoding().

バージョン 3.2 で追加.

exception tokenize.TokenError

docstring や複数行にわたることが許される式がファイル内のどこかで終わっていない場合に送出されます。例えば:

"""Beginning of
docstring

もしくは:

[1,
 2,
 3

閉じていないシングルクォート文字列は送出されるべきエラーの原因とならないことに注意してください。それらは ERRORTOKEN とトークン化され、続いてその内容がトークン化されます。

32.7.2. Command-Line Usage

バージョン 3.3 で追加.

The tokenize module can be executed as a script from the command line. It is as simple as:

python -m tokenize [-e] [filename.py]

The following options are accepted:

-h, --help

show this help message and exit

-e, --exact

display token names using the exact type

If filename.py is specified its contents are tokenized to stdout. Otherwise, tokenization is performed on stdin.

32.7.3. 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)

$ 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 -e option:

$ 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      ''