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A simple string scanner class for Python. Useful for building lexers/tokenizers by hand.

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README.rst

strscan

strscan.Scanner is a near-direct port of Ruby's StringScanner.

The aim is to provide for lexical scanning operations on strings:

>>> from strscan import Scanner
>>> s = Scanner("This is an example string")
>>> s.eos()
False
>>> s.scan(r'\w+')
'This'
>>> s.scan(r'\w+')
>>> s.scan(r'\s+')
' '
>>> s.scan(r'\s+')
>>> s.scan(r'\w+')
'is'
>>> s.eos()
False

>>> s.scan(r'\s+')
' '
>>> s.scan(r'\w+')
'an'
>>> s.scan(r'\s+')
' '
>>> s.scan(r'\w+')
'example'
>>> s.scan(r'\s+')
' '
>>> s.scan(r'\w+')
'string'
>>> s.eos()
True

>>> s.scan(r'\s+')
>>> s.scan(r'\w+')

Its mechanism of operation is similar to StringIO, only instead of reading by passing a number of bytes, you read by passing a regex. A scan pointer tracks the current position through the string, and all scanning or searching happens on the rest of the string after this pointer. scan is the simple case of reading some text and advancing the scan pointer, but there are several other related methods which fulfil different requirements.

All the methods on Scanner which take regexes will accept either regex strings or compiled pattern objects (as would be returned from re.compile()).

text_coords()

There's also a useful function provided, text_coords(), which resolves simple string indices into textual co-ordinates (line number and column):

>>> s = "abcdef\nghijkl\nmnopqr\nstuvwx\nyz"
>>> text_coords(s, 0)
(0, 0, 'abcdef')
>>> text_coords(s, 4)
(0, 4, 'abcdef')
>>> text_coords(s, 6)
(0, 6, 'abcdef')
>>> text_coords(s, 7)
(1, 0, 'ghijkl')
>>> text_coords(s, 11)
(1, 4, 'ghijkl')
>>> text_coords(s, 15)
(2, 1, 'mnopqr')

Installation

You can get the module from PyPI:

pip install strscan

(Un)license

This is free and unencumbered software released into the public domain.

Anyone is free to copy, modify, publish, use, compile, sell, or distribute this software, either in source code form or as a compiled binary, for any purpose, commercial or non-commercial, and by any means.

In jurisdictions that recognize copyright laws, the author or authors of this software dedicate any and all copyright interest in the software to the public domain. We make this dedication for the benefit of the public at large and to the detriment of our heirs and successors. We intend this dedication to be an overt act of relinquishment in perpetuity of all present and future rights to this software under copyright law.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

For more information, please refer to <http://unlicense.org/>

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