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implement loads more of format() spec

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implement closer to the format() spec
This commit is contained in:
Richard Jones
2011-11-18 10:44:55 +11:00
parent d26ba29b2d
commit 23b89610f7
5 changed files with 410 additions and 146 deletions
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MANIFEST.in
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@@ -1,2 +1,2 @@
include README.txt
include README.rst
include *.py
README.rst
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@@ -0,0 +1,88 @@
Parse strings using a specification based on the Python format() syntax.
parse() is the opposite of format()
The `Format String Syntax`_ is supported with anonymous (fixed-position),
named and formatted values are supported::
{[field name]:[format spec]}
Field names must be a single Python identifier word. No attributes or
element indexes are supported (as they would make no sense.)
Numbered fields are also not supported: the result of parsing will include
the parsed fields in the order they are parsed.
There conversion of values to types other than strings is not yet supported.
Some simple parse() format string examples:
>>> parse("Bring me a {}", "Bring me a shrubbery")
<Result ('shrubbery',) {}>
>>> parse("The {} who say {}", "The knights who say Ni!")
<Result ('knights', 'Ni!') {}>
>>> parse("Bring out the holy {item}", "Bring out the holy hand grenade")
<Result () {'item': 'hand grenade'}>
Most of the `Format Specification Mini-Language`_ is supported::
[[fill]align][sign][#][0][width][,][.precision][type]
The align operators will cause spaces (or specified fill character)
to be stripped from the value. The alignment character "=" is not yet
supported.
The comma "," separator is not yet supported.
The types supported are the not the format() types but rather some of
those types b, o, h, x, X and also regular expression character group types
d, D, w, W, s, S and not the string format types. The format() types n, f,
F, e, E, g and G are not yet supported.
===== ==========================================
Type Characters Matched
===== ==========================================
w Letters and underscore
W Non-letter and underscore
s Whitespace
S Non-whitespace
d Digits (effectively integer numbers)
D Non-digit
b Binary numbers
o Octal numbers
h Hexadecimal numbers (lower and upper case)
x Lower-case hexadecimal numbers
X Upper-case hexadecimal numbers
===== ==========================================
Do remember though that most often a straight type-less {} will suffice
where a more complex type specification might have been used.
So, for example, some typed parsing, and None resulting if the typing
does not match:
>>> parse('Hello {:d} {:w}', 'Hello 12 people')
<Result ('12', 'people') {}>
>>> print parse('Hello {:d} {:w}', 'Hello twelve people')
None
And messing about with alignment:
>>> parse('hello {:<} world', 'hello there world')
<Result ('there',) {}>
>>> parse('hello {:^} world', 'hello there world')
<Result ('there',) {}>
Note that the "center" alignment does not test to make sure the value is
actually centered. It just strips leading and trailing whitespace.
See also the unit tests at the end of the module for some more
examples. Run the tests with "python -m parse".
.. _`Format String Syntax`: http://docs.python.org/library/string.html#format-string-syntax
.. _`Format Specification Mini-Language`: http://docs.python.org/library/string.html#format-specification-mini-language
----
This code is copyright 2011 eKit.com Inc (http://www.ekit.com/)
See the end of the source file for the license of use.
README.txt
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@@ -1,44 +0,0 @@
Parse strings using a specification based on the Python format() syntax.
Anonymous (fixed-position), named and typed values are supported. Also the
alignment operators will cause whitespace (or another alignment character)
to be stripped from the value.
You may not use both fixed and named values in your format string.
The types supported in ":type" expressions are the regular expression
character group types d, D, w, W, s, S and not the string format types.
So, for example, some fixed-position parsing:
>>> r = parse('hello {}', 'hello world')
>>> r.fixed
('world', )
>>> r = parse('hello {:d} {:w}', 'hello 12 people')
>>> r.fixed
('12', 'people')
And some named parsing:
>>> r = parse('{greeting} {name}', 'hello world')
>>> r.named
{'greeting': 'hello', 'name': 'world'}
>>> r = parse('hello {^} world', 'hello there world')
>>> r.fixed
('there', )
None will be returned if there is no match:
>>> r = parse('hello {name:w}', 'hello 12')
>>> print r
None
See also the unit tests at the end of the module for some more
examples. Run those with "python -m parse".
----
This code is copyright 2011 eKit.com Inc (http://www.ekit.com/)
See the end of the source file for the license of use.
parse.py
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@@ -4,50 +4,94 @@
#
'''Parse strings using a specification based on the Python format() syntax.
Anonymous (fixed-position), named and typed values are supported. Also the
alignment operators will cause whitespace (or another alignment character)
to be stripped from the value.
parse() is the opposite of format()
You may not use both fixed and named values in your format string.
The `Format String Syntax`_ is supported with anonymous (fixed-position),
named and formatted values are supported::
The types supported in ":type" expressions are the regular expression
character group types d, D, w, W, s, S and not the string format types.
{[field name]:[format spec]}
So, for example, some fixed-position parsing:
Field names must be a single Python identifier word. No attributes or
element indexes are supported (as they would make no sense.)
>>> r = parse('hello {}', 'hello world')
>>> r.fixed
('world', )
Numbered fields are also not supported: the result of parsing will include
the parsed fields in the order they are parsed.
>>> r = parse('hello {:d} {:w}', 'hello 12 people')
>>> r.fixed
('12', 'people')
There conversion of values to types other than strings is not yet supported.
And some named parsing:
Some simple parse() format string examples:
>>> r = parse('{greeting} {name}', 'hello world')
>>> r.named
{'greeting': 'hello', 'name': 'world'}
>>> parse("Bring me a {}", "Bring me a shrubbery")
<Result ('shrubbery',) {}>
>>> parse("The {} who say {}", "The knights who say Ni!")
<Result ('knights', 'Ni!') {}>
>>> parse("Bring out the holy {item}", "Bring out the holy hand grenade")
<Result () {'item': 'hand grenade'}>
>>> r = parse('hello {^} world', 'hello there world')
>>> r.fixed
('there', )
Most of the `Format Specification Mini-Language`_ is supported::
None will be returned if there is no match:
[[fill]align][sign][#][0][width][,][.precision][type]
>>> r = parse('hello {name:w}', 'hello 12')
>>> print r
The align operators will cause spaces (or specified fill character)
to be stripped from the value. The alignment character "=" is not yet
supported.
The comma "," separator is not yet supported.
The types supported are the not the format() types but rather some of
those types b, o, h, x, X and also regular expression character group types
d, D, w, W, s, S and not the string format types. The format() types n, f,
F, e, E, g and G are not yet supported.
===== ==========================================
Type Characters Matched
===== ==========================================
w Letters and underscore
W Non-letter and underscore
s Whitespace
S Non-whitespace
d Digits (effectively integer numbers)
D Non-digit
b Binary numbers
o Octal numbers
h Hexadecimal numbers (lower and upper case)
x Lower-case hexadecimal numbers
X Upper-case hexadecimal numbers
===== ==========================================
Do remember though that most often a straight type-less {} will suffice
where a more complex type specification might have been used.
So, for example, some typed parsing, and None resulting if the typing
does not match:
>>> parse('Hello {:d} {:w}', 'Hello 12 people')
<Result ('12', 'people') {}>
>>> print parse('Hello {:d} {:w}', 'Hello twelve people')
None
And messing about with alignment:
>>> parse('hello {:<} world', 'hello there world')
<Result ('there',) {}>
>>> parse('hello {:^} world', 'hello there world')
<Result ('there',) {}>
Note that the "center" alignment does not test to make sure the value is
actually centered. It just strips leading and trailing whitespace.
See also the unit tests at the end of the module for some more
examples. Run those with "python -m parse".
examples. Run the tests with "python -m parse".
.. _`Format String Syntax`: http://docs.python.org/library/string.html#format-string-syntax
.. _`Format Specification Mini-Language`: http://docs.python.org/library/string.html#format-specification-mini-language
----
This code is copyright 2011 eKit.com Inc (http://www.ekit.com/)
See the end of the source file for the license of use.
'''
__version__ = '1.0.0'
__version__ = '1.1.0'
import re
import unittest
@@ -61,52 +105,159 @@ PARSE_RE = re.compile('''
|
(?P<closebrace>}})
|
(?P<fixed>{(?P<falign>[^}]?[<>^])?(:[^}]+?)?})
(?P<fixed>{(:[^}]+?)?})
|
{(?P<nalign>[^}]?[<>^])?(?P<named>\w+(:[^}]+?)?)}
{(?P<named>\w+(:[^}]+?)?)}
)''', re.VERBOSE)
class Format(object):
# we're an object so we can keep track of whether the user is trying to
# specify both fixed and named args
has_fixed = False
has_named = False
# three problems?
FORMAT_RE = re.compile('''
(?P<align>(?P<fill>[^}])?[<>^])?
(?P<sign>[-+ ])?
(?P<prefix>\#)?
(?P<width>(?P<zero>0)?[1-9]\d*)?
(\.(?P<precision>\d+))?
(?P<type>[bohxXwWdDsS])?
''', re.VERBOSE)
class Result(object):
def __init__(self):
self._fixed_args = []
self._groups = 0
self.fixed = ()
self.named = {}
def __repr__(self):
return '<Result %r %r>' % (self.fixed, self.named)
@classmethod
def parse(cls, format, string):
o = cls()
# first, turn the format into a regular expression
r = PARSE_RE.sub(o.replace, format)
m = re.match('^' + r + '$', string)
if m is None:
return None
l = m.groups()
o.named = m.groupdict()
o.fixed = tuple(l[n] for n in o._fixed_args)
return o
def replace(self, match):
d = match.groupdict()
if d['openbrace']: return '{{'
if d['closebrace']: return '}}'
align = None
if d['openbrace']: return '{'
if d['closebrace']: return '}'
format = ''
#print 'PARSE', d
if d['fixed']:
if self.has_named:
raise ValueError("can't mix named and fixed")
self.has_fixed = True
self._fixed_args.append(self._groups)
wrap = '(%s)'
if ':' in d['fixed']:
x, type = d['fixed'].split(':')
s = r'(\%s+?)' % type[:1]
format = d['fixed'][2:-1]
elif d['named']:
if ':' in d['named']:
name, format = d['named'].split(':')
else:
s = r'(.+?)'
align = d['falign']
name = d['named']
wrap = '(?P<%s>%%s)' % name
else:
raise ValueError('format not recognised')
if d['named']:
if self.has_fixed:
raise ValueError("can't mix named and fixed")
self.has_named = True
if ':' not in d['named']:
s = r'(?P<%s>.+?)' % d['named']
self._groups += 1
if not format:
return wrap % '.+?'
m = FORMAT_RE.match(format)
if m is None:
raise ValueError('format %r not recognised' % format)
d = m.groupdict()
#print 'FORMAT', d
if d['type'] == 'o':
s = '[0-7]'
elif d['type'] == 'b':
s = '[01]'
elif d['type'] == 'h':
s = '[0-9a-fA-F]'
elif d['type'] == 'x':
s = '[0-9a-f]'
elif d['type'] == 'X':
s = '[0-9A-F]'
elif d['type']:
s = r'\%s' % d['type']
else:
s = '.'
# TODO: number types still to support:
# n Number (with number separator characters)
# f Floating-point numbers
# e Exponent notation
# E Exponent notation with upper-case E
# g General number format with added nan, inf and -inf
# G General number format with upper-case E, NAN, INF and -INF
if d['type'] and d['type'] in 'dobhxX':
if d['prefix']:
if d['type'] == 'b':
s = '0b' + s
elif d['type'] == 'o':
s = '0o' + s
elif d['type'] in 'hxX':
s = '0x' + s
else:
raise ValueError('prefix # not compatible with type %s' %
d['type'])
if not d['sign']:
# default sign handling
s = r'-?' + s
elif d['sign'] == '+':
s = r'[-+]?' + s
elif d['sign'] == '-':
s = r'-?' + s
elif d['sign'] == ' ':
s = r'[- ]?' + s
else:
name, type = d['named'].split(':')
s = r'(?P<%s>\%s+?)' % (name, type)
align = d['nalign']
raise ValueError('sign in format "%s" unrecognised' % d['sign'])
else:
if d['prefix']:
raise ValueError('prefix # in format must accompany numeric type')
if d['sign']:
raise ValueError('sign in format must accompany "d" type')
if not align:
return s
if d['width']:
if d['zero']:
s = s + '{%s}' % d['width'][1:]
else:
s = s + '{%s}' % d['width']
else:
s = s + '+?'
if len(align) == 2:
fill, align = align
s = wrap % s
if d['zero']:
s = '0*' + s
# TODO handle precision
#(\.(?P<precision>\d+))?
# TODO support '='
align = d['align']
fill = d['fill']
if fill:
align = align[1]
else:
fill = ' '
if fill in '.\+?*[](){}^$':
fill = '\\' + fill
if align == '<':
@@ -118,9 +269,6 @@ class Format(object):
return s
Result = collections.namedtuple('Result', 'fixed named')
def parse(format, string):
'''Using "format" attempt to pull values from "string".
@@ -129,83 +277,98 @@ def parse(format, string):
.fixed - tuple of fixed-position values from the string
.named - dict of named values from the string
If the format is invalid (usually mixing fixed-position and named values
in the format) a ValueError will be raised.
If the format is invalid a ValueError will be raised.
In the case there is no match parse() will return None.
'''
# first, turn the format into a regular expression
r = PARSE_RE.sub(Format().replace, format)
m = re.match('^' + r + '$', string)
if m is None:
return None
d = m.groupdict()
if d:
return Result(None, d)
else:
return Result(m.groups(), None)
return Result().parse(format, string)
# yes, I now unit test both of the problems
class TestPattern(unittest.TestCase):
def test_mixed(self):
'check enforcement of fixed OR named'
self.assertRaises(ValueError, PARSE_RE.sub, Format().replace,
'{} {name}')
def test_braces(self):
'pull a simple string out of another string'
s = PARSE_RE.sub(Format().replace, '{{ }}')
self.assertEquals(s, '{{ }}')
s = PARSE_RE.sub(Result().replace, '{{ }}')
self.assertEquals(s, '{ }')
def test_fixed(self):
'pull a simple string out of another string'
s = PARSE_RE.sub(Format().replace, '{}')
s = PARSE_RE.sub(Result().replace, '{}')
self.assertEquals(s, '(.+?)')
s = PARSE_RE.sub(Format().replace, '{} {}')
s = PARSE_RE.sub(Result().replace, '{} {}')
self.assertEquals(s, '(.+?) (.+?)')
def test_typed(self):
'pull a named string out of another string'
s = PARSE_RE.sub(Format().replace, '{:d}')
self.assertEquals(s, '(\d+?)')
s = PARSE_RE.sub(Format().replace, '{:d} {:w}')
self.assertEquals(s, '(\d+?) (\w+?)')
s = PARSE_RE.sub(Result().replace, '{:d}')
self.assertEquals(s, '(-?\d+?)')
s = PARSE_RE.sub(Result().replace, '{:d} {:w}')
self.assertEquals(s, '(-?\d+?) (\w+?)')
def test_named(self):
'pull a named string out of another string'
s = PARSE_RE.sub(Format().replace, '{name}')
s = PARSE_RE.sub(Result().replace, '{name}')
self.assertEquals(s, '(?P<name>.+?)')
s = PARSE_RE.sub(Format().replace, '{name} {other}')
s = PARSE_RE.sub(Result().replace, '{name} {other}')
self.assertEquals(s, '(?P<name>.+?) (?P<other>.+?)')
def test_named_typed(self):
'pull a named string out of another string'
s = PARSE_RE.sub(Format().replace, '{name:d}')
self.assertEquals(s, '(?P<name>\d+?)')
s = PARSE_RE.sub(Format().replace, '{name:d} {other:w}')
self.assertEquals(s, '(?P<name>\d+?) (?P<other>\w+?)')
s = PARSE_RE.sub(Result().replace, '{name:d}')
self.assertEquals(s, '(?P<name>-?\d+?)')
s = PARSE_RE.sub(Result().replace, '{name:d} {other:w}')
self.assertEquals(s, '(?P<name>-?\d+?) (?P<other>\w+?)')
def test_left(self):
def test_beaker(self):
'skip some trailing whitespace'
s = PARSE_RE.sub(Format().replace, '{<}')
s = PARSE_RE.sub(Result().replace, '{:<}')
self.assertEquals(s, '(.+?) +')
def test_left_fill(self):
'skip some trailing periods'
s = PARSE_RE.sub(Format().replace, '{.<}')
s = PARSE_RE.sub(Result().replace, '{:.<}')
self.assertEquals(s, '(.+?)\.+')
def test_right(self):
def test_bird(self):
'skip some trailing whitespace'
s = PARSE_RE.sub(Format().replace, '{>}')
s = PARSE_RE.sub(Result().replace, '{:>}')
self.assertEquals(s, ' +(.+?)')
def test_center(self):
'skip some surrounding whitespace'
s = PARSE_RE.sub(Format().replace, '{^}')
s = PARSE_RE.sub(Result().replace, '{:^}')
self.assertEquals(s, ' +(.+?) +')
def test_format(self):
def _(fmt, matches):
m = FORMAT_RE.match(fmt)
self.assertNotEquals(m, None,
'FORMAT_RE failed to parse %r' % fmt)
d = m.groupdict()
for k in matches:
self.assertEquals(d.get(k), matches[k],
'm["%s"]=%r, expect %r' % (k, d.get(k), matches[k]))
for t in 'obhdDwWsS':
_(t, dict(type=t))
_('10'+t, dict(type=t, width='10'))
_('05d', dict(type='d', width='05', zero='0'))
_('#d', dict(type='d', prefix='#'))
_('<', dict(align='<'))
_('.<', dict(align='.<', fill='.'))
_('>', dict(align='>'))
_('.>', dict(align='.>', fill='.'))
_('^', dict(align='^'))
_('.^', dict(align='.^', fill='.'))
_('d', dict(type='d'))
_('-d', dict(type='d', sign='-'))
_('+d', dict(type='d', sign='+'))
_(' d', dict(type='d', sign=' '))
_('.^+#010d', dict(type='d', width='010', align='.^', fill='.', prefix='#',
sign='+', zero='0'))
#(\.(?P<precision>\d+))?
class TestParse(unittest.TestCase):
def test_no_match(self):
@@ -214,9 +377,9 @@ class TestParse(unittest.TestCase):
def test_nothing(self):
'do no actual parsing'
r = parse('{{hello}}', '{{hello}}')
r = parse('{{hello}}', '{hello}')
self.assertEquals(r.fixed, ())
self.assertEquals(r.named, None)
self.assertEquals(r.named, {})
def test_fixed(self):
'pull a fixed value out of string'
@@ -225,17 +388,17 @@ class TestParse(unittest.TestCase):
def test_left(self):
'pull left-aligned text out of string'
r = parse('{<} world', 'hello world')
r = parse('{:<} world', 'hello world')
self.assertEquals(r.fixed, ('hello', ))
def test_right(self):
'pull right-aligned text out of string'
r = parse('hello {>}', 'hello world')
r = parse('hello {:>}', 'hello world')
self.assertEquals(r.fixed, ('world', ))
def test_center(self):
'pull right-aligned text out of string'
r = parse('hello {^} world', 'hello there world')
r = parse('hello {:^} world', 'hello there world')
self.assertEquals(r.fixed, ('there', ))
def test_typed(self):
@@ -252,11 +415,64 @@ class TestParse(unittest.TestCase):
r = parse('hello {name}', 'hello world')
self.assertEquals(r.named, {'name': 'world'})
def test_mixed(self):
'pull a fixed and named values out of string'
r = parse('hello {} {name} {} {spam}', 'hello world and other beings')
self.assertEquals(r.fixed, ('world', 'other'))
self.assertEquals(r.named, dict(name='and', spam='beings'))
def test_named_typed(self):
'pull a named, typed values out of string'
r = parse('hello {number:d} {things}', 'hello 12 people')
self.assertEquals(r.named, dict(number='12', things='people'))
def test_named_aligned_typed(self):
'pull a named, typed values out of string'
r = parse('hello {number:<d} {things}', 'hello 12 people')
self.assertEquals(r.named, dict(number='12', things='people'))
r = parse('hello {number:>d} {things}', 'hello 12 people')
self.assertEquals(r.named, dict(number='12', things='people'))
r = parse('hello {number:^d} {things}', 'hello 12 people')
self.assertEquals(r.named, dict(number='12', things='people'))
def test_numbers(self):
'pull a numbers out of a string'
def y(fmt, s, e):
r = parse(fmt, s)
if r is None: self.fail('%r did not match %r' % (fmt, s))
self.assertEquals(r.fixed[0], e,
'%r found %r in %r, not %r' % (fmt, r.fixed[0], s, e))
def n(fmt, s, e):
if parse(fmt, s) is not None:
self.fail('%r matched %r' % (fmt, s))
y('a {:d} b', 'a 12 b', '12')
y('a {:d} b', 'a -12 b', '-12')
n('a {:d} b', 'a +12 b', None)
y('a {:-d} b', 'a -12 b', '-12')
n('a {:-d} b', 'a +12 b', None)
y('a {:+d} b', 'a -12 b', '-12')
y('a {:+d} b', 'a +12 b', '+12')
y('a {: d} b', 'a -12 b', '-12')
y('a {: d} b', 'a 12 b', ' 12')
n('a {: d} b', 'a +12 b', None)
y('a {:b} b', 'a 101101 b', '101101')
y('a {:#b} b', 'a 0b101101 b', '0b101101')
y('a {:o} b', 'a 12345670 b', '12345670')
y('a {:#o} b', 'a 0o12345670 b', '0o12345670')
y('a {:h} b', 'a 1234567890abcdef b', '1234567890abcdef')
y('a {:h} b', 'a 1234567890ABCDEF b', '1234567890ABCDEF')
y('a {:#h} b', 'a 0x1234567890abcdef b', '0x1234567890abcdef')
y('a {:#h} b', 'a 0x1234567890ABCDEF b', '0x1234567890ABCDEF')
y('a {:x} b', 'a 1234567890abcdef b', '1234567890abcdef')
y('a {:X} b', 'a 1234567890ABCDEF b', '1234567890ABCDEF')
y('a {:#x} b', 'a 0x1234567890abcdef b', '0x1234567890abcdef')
y('a {:#X} b', 'a 0x1234567890ABCDEF b', '0x1234567890ABCDEF')
y('a {:05d} b', 'a 00001 b', '00001')
# TODO this should pass
# y('a {:05d} b', 'a 0000001 b', None)
if __name__ == '__main__':
unittest.main()
@@ -281,3 +497,4 @@ if __name__ == '__main__':
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
# SOFTWARE.
# vim: set filetype=python ts=4 sw=4 et si tw=75
setup.py
+4 -1
View File
@@ -4,11 +4,14 @@ from distutils.core import setup
from parse import __version__, __doc__
with open('README.rst', 'w') as f:
f.write(__doc__)
# perform the setup action
setup(
name = "parse",
version = __version__,
description = "Parse strings using a specification based on the Python format() syntax.",
description = "parse() is the opposite of format()",
long_description = __doc__.decode('utf8'),
author = "Richard Jones",
author_email = "rjones@ekit-inc.com",