Viewing file:  cssselect.py (29.6 KB) -rw-r--r--
Select action/file-type:
 (+) |  (+) |  (+) | Code (+) | Session (+) |  (+) | SDB (+) |  (+) |  (+) |  (+) |  (+) |  (+) |
"""CSS Selectors based on XPath.
This module supports selecting XML/HTML tags based on CSS selectors.
See the `CSSSelector` class for details.
"""
import re
from lxml import etree
__all__ = ['SelectorSyntaxError', 'ExpressionError',
'CSSSelector']
try:
_basestring = basestring
except NameError:
_basestring = str
class SelectorSyntaxError(SyntaxError):
pass
class ExpressionError(RuntimeError):
pass
class CSSSelector(etree.XPath):
"""A CSS selector.
Usage::
>>> from lxml import etree, cssselect
>>> select = cssselect.CSSSelector("a tag > child")
>>> root = etree.XML("<a><b><c/><tag><child>TEXT</child></tag></b></a>")
>>> [ el.tag for el in select(root) ]
['child']
"""
def __init__(self, css):
path = css_to_xpath(css)
etree.XPath.__init__(self, path)
self.css = css
def __repr__(self):
return '<%s %s for %r>' % (
self.__class__.__name__,
hex(abs(id(self)))[2:],
self.css)
##############################
## Token objects:
try:
_unicode = unicode
_unichr = unichr
except NameError:
# Python 3
_unicode = str
_unichr = chr
class _UniToken(_unicode):
def __new__(cls, contents, pos):
obj = _unicode.__new__(cls, contents)
obj.pos = pos
return obj
def __repr__(self):
return '%s(%s, %r)' % (
self.__class__.__name__,
_unicode.__repr__(self),
self.pos)
class Symbol(_UniToken):
pass
class String(_UniToken):
pass
class Token(_UniToken):
pass
############################################################
## Parsing
############################################################
##############################
## Syntax objects:
class Class(object):
"""
Represents selector.class_name
"""
def __init__(self, selector, class_name):
self.selector = selector
self.class_name = class_name
def __repr__(self):
return '%s[%r.%s]' % (
self.__class__.__name__,
self.selector,
self.class_name)
def xpath(self):
sel_xpath = self.selector.xpath()
sel_xpath.add_condition(
"contains(concat(' ', normalize-space(@class), ' '), %s)" % xpath_literal(' '+self.class_name+' '))
return sel_xpath
class Function(object):
"""
Represents selector:name(expr)
"""
unsupported = [
'target', 'lang', 'enabled', 'disabled',]
def __init__(self, selector, type, name, expr):
self.selector = selector
self.type = type
self.name = name
self.expr = expr
def __repr__(self):
return '%s[%r%s%s(%r)]' % (
self.__class__.__name__,
self.selector,
self.type, self.name, self.expr)
def xpath(self):
sel_path = self.selector.xpath()
if self.name in self.unsupported:
raise ExpressionError(
"The psuedo-class %r is not supported" % self.name)
method = '_xpath_' + self.name.replace('-', '_')
if not hasattr(self, method):
raise ExpressionError(
"The psuedo-class %r is unknown" % self.name)
method = getattr(self, method)
return method(sel_path, self.expr)
def _xpath_nth_child(self, xpath, expr, last=False,
add_name_test=True):
a, b = parse_series(expr)
if not a and not b and not last:
# a=0 means nothing is returned...
xpath.add_condition('false() and position() = 0')
return xpath
if add_name_test:
xpath.add_name_test()
xpath.add_star_prefix()
if a == 0:
if last:
b = 'last() - %s' % b
xpath.add_condition('position() = %s' % b)
return xpath
if last:
# FIXME: I'm not sure if this is right
a = -a
b = -b
if b > 0:
b_neg = str(-b)
else:
b_neg = '+%s' % (-b)
if a != 1:
expr = ['(position() %s) mod %s = 0' % (b_neg, a)]
else:
expr = []
if b >= 0:
expr.append('position() >= %s' % b)
elif b < 0 and last:
expr.append('position() < (last() %s)' % b)
expr = ' and '.join(expr)
if expr:
xpath.add_condition(expr)
return xpath
# FIXME: handle an+b, odd, even
# an+b means every-a, plus b, e.g., 2n+1 means odd
# 0n+b means b
# n+0 means a=1, i.e., all elements
# an means every a elements, i.e., 2n means even
# -n means -1n
# -1n+6 means elements 6 and previous
def _xpath_nth_last_child(self, xpath, expr):
return self._xpath_nth_child(xpath, expr, last=True)
def _xpath_nth_of_type(self, xpath, expr):
if xpath.element == '*':
raise NotImplementedError(
"*:nth-of-type() is not implemented")
return self._xpath_nth_child(xpath, expr, add_name_test=False)
def _xpath_nth_last_of_type(self, xpath, expr):
return self._xpath_nth_child(xpath, expr, last=True, add_name_test=False)
def _xpath_contains(self, xpath, expr):
# text content, minus tags, must contain expr
if isinstance(expr, Element):
expr = expr._format_element()
xpath.add_condition('contains(css:lower-case(string(.)), %s)'
% xpath_literal(expr.lower()))
# FIXME: Currently case insensitive matching doesn't seem to be happening
return xpath
def _xpath_not(self, xpath, expr):
# everything for which not expr applies
expr = expr.xpath()
cond = expr.condition
# FIXME: should I do something about element_path?
xpath.add_condition('not(%s)' % cond)
return xpath
def _make_lower_case(context, s):
return s.lower()
ns = etree.FunctionNamespace('http://codespeak.net/lxml/css/')
ns.prefix = 'css'
ns['lower-case'] = _make_lower_case
class Pseudo(object):
"""
Represents selector:ident
"""
unsupported = ['indeterminate', 'first-line', 'first-letter',
'selection', 'before', 'after', 'link', 'visited',
'active', 'focus', 'hover']
def __init__(self, element, type, ident):
self.element = element
assert type in (':', '::')
self.type = type
self.ident = ident
def __repr__(self):
return '%s[%r%s%s]' % (
self.__class__.__name__,
self.element,
self.type, self.ident)
def xpath(self):
el_xpath = self.element.xpath()
if self.ident in self.unsupported:
raise ExpressionError(
"The psuedo-class %r is unsupported" % self.ident)
method = '_xpath_' + self.ident.replace('-', '_')
if not hasattr(self, method):
raise ExpressionError(
"The psuedo-class %r is unknown" % self.ident)
method = getattr(self, method)
el_xpath = method(el_xpath)
return el_xpath
def _xpath_checked(self, xpath):
# FIXME: is this really all the elements?
xpath.add_condition("(@selected or @checked) and (name(.) = 'input' or name(.) = 'option')")
return xpath
def _xpath_root(self, xpath):
# if this element is the root element
raise NotImplementedError
def _xpath_first_child(self, xpath):
xpath.add_star_prefix()
xpath.add_name_test()
xpath.add_condition('position() = 1')
return xpath
def _xpath_last_child(self, xpath):
xpath.add_star_prefix()
xpath.add_name_test()
xpath.add_condition('position() = last()')
return xpath
def _xpath_first_of_type(self, xpath):
if xpath.element == '*':
raise NotImplementedError(
"*:first-of-type is not implemented")
xpath.add_star_prefix()
xpath.add_condition('position() = 1')
return xpath
def _xpath_last_of_type(self, xpath):
if xpath.element == '*':
raise NotImplementedError(
"*:last-of-type is not implemented")
xpath.add_star_prefix()
xpath.add_condition('position() = last()')
return xpath
def _xpath_only_child(self, xpath):
xpath.add_name_test()
xpath.add_star_prefix()
xpath.add_condition('last() = 1')
return xpath
def _xpath_only_of_type(self, xpath):
if xpath.element == '*':
raise NotImplementedError(
"*:only-of-type is not implemented")
xpath.add_condition('last() = 1')
return xpath
def _xpath_empty(self, xpath):
xpath.add_condition("not(*) and not(normalize-space())")
return xpath
class Attrib(object):
"""
Represents selector[namespace|attrib operator value]
"""
def __init__(self, selector, namespace, attrib, operator, value):
self.selector = selector
self.namespace = namespace
self.attrib = attrib
self.operator = operator
self.value = value
def __repr__(self):
if self.operator == 'exists':
return '%s[%r[%s]]' % (
self.__class__.__name__,
self.selector,
self._format_attrib())
else:
return '%s[%r[%s %s %r]]' % (
self.__class__.__name__,
self.selector,
self._format_attrib(),
self.operator,
self.value)
def _format_attrib(self):
if self.namespace == '*':
return self.attrib
else:
return '%s|%s' % (self.namespace, self.attrib)
def _xpath_attrib(self):
# FIXME: if attrib is *?
if self.namespace == '*':
return '@' + self.attrib
else:
return '@%s:%s' % (self.namespace, self.attrib)
def xpath(self):
path = self.selector.xpath()
attrib = self._xpath_attrib()
value = self.value
if self.operator == 'exists':
assert not value
path.add_condition(attrib)
elif self.operator == '=':
path.add_condition('%s = %s' % (attrib,
xpath_literal(value)))
elif self.operator == '!=':
# FIXME: this seems like a weird hack...
if value:
path.add_condition('not(%s) or %s != %s'
% (attrib, attrib, xpath_literal(value)))
else:
path.add_condition('%s != %s'
% (attrib, xpath_literal(value)))
#path.add_condition('%s != %s' % (attrib, xpath_literal(value)))
elif self.operator == '~=':
path.add_condition("contains(concat(' ', normalize-space(%s), ' '), %s)" % (attrib, xpath_literal(' '+value+' ')))
elif self.operator == '|=':
# Weird, but true...
path.add_condition('%s = %s or starts-with(%s, %s)' % (
attrib, xpath_literal(value),
attrib, xpath_literal(value + '-')))
elif self.operator == '^=':
path.add_condition('starts-with(%s, %s)' % (
attrib, xpath_literal(value)))
elif self.operator == '$=':
# Oddly there is a starts-with in XPath 1.0, but not ends-with
path.add_condition('substring(%s, string-length(%s)-%s) = %s'
% (attrib, attrib, len(value)-1, xpath_literal(value)))
elif self.operator == '*=':
# FIXME: case sensitive?
path.add_condition('contains(%s, %s)' % (
attrib, xpath_literal(value)))
else:
assert 0, ("Unknown operator: %r" % self.operator)
return path
class Element(object):
"""
Represents namespace|element
"""
def __init__(self, namespace, element):
self.namespace = namespace
self.element = element
def __repr__(self):
return '%s[%s]' % (
self.__class__.__name__,
self._format_element())
def _format_element(self):
if self.namespace == '*':
return self.element
else:
return '%s|%s' % (self.namespace, self.element)
def xpath(self):
if self.namespace == '*':
el = self.element.lower()
else:
# FIXME: Should we lowercase here?
el = '%s:%s' % (self.namespace, self.element)
return XPathExpr(element=el)
class Hash(object):
"""
Represents selector#id
"""
def __init__(self, selector, id):
self.selector = selector
self.id = id
def __repr__(self):
return '%s[%r#%s]' % (
self.__class__.__name__,
self.selector, self.id)
def xpath(self):
path = self.selector.xpath()
path.add_condition('@id = %s' % xpath_literal(self.id))
return path
class Or(object):
def __init__(self, items):
self.items = items
def __repr__(self):
return '%s(%r)' % (
self.__class__.__name__,
self.items)
def xpath(self):
paths = [item.xpath() for item in self.items]
return XPathExprOr(paths)
class CombinedSelector(object):
_method_mapping = {
' ': 'descendant',
'>': 'child',
'+': 'direct_adjacent',
'~': 'indirect_adjacent',
}
def __init__(self, selector, combinator, subselector):
assert selector is not None
self.selector = selector
self.combinator = combinator
self.subselector = subselector
def __repr__(self):
if self.combinator == ' ':
comb = '<followed>'
else:
comb = self.combinator
return '%s[%r %s %r]' % (
self.__class__.__name__,
self.selector,
comb,
self.subselector)
def xpath(self):
if self.combinator not in self._method_mapping:
raise ExpressionError(
"Unknown combinator: %r" % self.combinator)
method = '_xpath_' + self._method_mapping[self.combinator]
method = getattr(self, method)
path = self.selector.xpath()
return method(path, self.subselector)
def _xpath_descendant(self, xpath, sub):
# when sub is a descendant in any way of xpath
xpath.join('/descendant::', sub.xpath())
return xpath
def _xpath_child(self, xpath, sub):
# when sub is an immediate child of xpath
xpath.join('/', sub.xpath())
return xpath
def _xpath_direct_adjacent(self, xpath, sub):
# when sub immediately follows xpath
xpath.join('/following-sibling::', sub.xpath())
xpath.add_name_test()
xpath.add_condition('position() = 1')
return xpath
def _xpath_indirect_adjacent(self, xpath, sub):
# when sub comes somewhere after xpath as a sibling
xpath.join('/following-sibling::', sub.xpath())
return xpath
##############################
## XPathExpr objects:
_el_re = re.compile(r'^\w+\s*$', re.UNICODE)
_id_re = re.compile(r'^(\w*)#(\w+)\s*$', re.UNICODE)
_class_re = re.compile(r'^(\w*)\.(\w+)\s*$', re.UNICODE)
def css_to_xpath(css_expr, prefix='descendant-or-self::'):
if isinstance(css_expr, _basestring):
match = _el_re.search(css_expr)
if match is not None:
return '%s%s' % (prefix, match.group(0).strip())
match = _id_re.search(css_expr)
if match is not None:
return "%s%s[@id = '%s']" % (
prefix, match.group(1) or '*', match.group(2))
match = _class_re.search(css_expr)
if match is not None:
return "%s%s[contains(concat(' ', normalize-space(@class), ' '), ' %s ')]" % (
prefix, match.group(1) or '*', match.group(2))
css_expr = parse(css_expr)
expr = css_expr.xpath()
assert expr is not None, (
"Got None for xpath expression from %s" % repr(css_expr))
if prefix:
expr.add_prefix(prefix)
return _unicode(expr)
class XPathExpr(object):
def __init__(self, prefix=None, path=None, element='*', condition=None,
star_prefix=False):
self.prefix = prefix
self.path = path
self.element = element
self.condition = condition
self.star_prefix = star_prefix
def __str__(self):
path = ''
if self.prefix is not None:
path += _unicode(self.prefix)
if self.path is not None:
path += _unicode(self.path)
path += _unicode(self.element)
if self.condition:
path += '[%s]' % self.condition
return path
def __repr__(self):
return '%s[%s]' % (
self.__class__.__name__, self)
def add_condition(self, condition):
if self.condition:
self.condition = '%s and (%s)' % (self.condition, condition)
else:
self.condition = condition
def add_path(self, part):
if self.path is None:
self.path = self.element
else:
self.path += self.element
self.element = part
def add_prefix(self, prefix):
if self.prefix:
self.prefix = prefix + self.prefix
else:
self.prefix = prefix
def add_name_test(self):
if self.element == '*':
# We weren't doing a test anyway
return
self.add_condition("name() = %s" % xpath_literal(self.element))
self.element = '*'
def add_star_prefix(self):
"""
Adds a /* prefix if there is no prefix. This is when you need
to keep context's constrained to a single parent.
"""
if self.path:
self.path += '*/'
else:
self.path = '*/'
self.star_prefix = True
def join(self, combiner, other):
prefix = _unicode(self)
prefix += combiner
path = (other.prefix or '') + (other.path or '')
# We don't need a star prefix if we are joining to this other
# prefix; so we'll get rid of it
if other.star_prefix and path == '*/':
path = ''
self.prefix = prefix
self.path = path
self.element = other.element
self.condition = other.condition
class XPathExprOr(XPathExpr):
"""
Represents |'d expressions. Note that unfortunately it isn't
the union, it's the sum, so duplicate elements will appear.
"""
def __init__(self, items, prefix=None):
for item in items:
assert item is not None
self.items = items
self.prefix = prefix
def __str__(self):
prefix = self.prefix or ''
return ' | '.join(["%s%s" % (prefix,i) for i in self.items])
split_at_single_quotes = re.compile("('+)").split
def xpath_literal(s):
if isinstance(s, Element):
# This is probably a symbol that looks like an expression...
s = s._format_element()
else:
s = _unicode(s)
if "'" not in s:
s = "'%s'" % s
elif '"' not in s:
s = '"%s"' % s
else:
s = "concat(%s)" % ','.join([
(("'" in part) and '"%s"' or "'%s'") % part
for part in split_at_single_quotes(s) if part
])
return s
##############################
## Parsing functions
def parse(string):
stream = TokenStream(tokenize(string))
stream.source = string
try:
return parse_selector_group(stream)
except SelectorSyntaxError:
import sys
e = sys.exc_info()[1]
message = "%s at %s -> %r" % (
e, stream.used, stream.peek())
e.msg = message
if sys.version_info < (2,6):
e.message = message
e.args = tuple([message])
raise
def parse_selector_group(stream):
result = []
while 1:
result.append(parse_selector(stream))
if stream.peek() == ',':
stream.next()
else:
break
if len(result) == 1:
return result[0]
else:
return Or(result)
def parse_selector(stream):
result = parse_simple_selector(stream)
while 1:
peek = stream.peek()
if peek == ',' or peek is None:
return result
elif peek in ('+', '>', '~'):
# A combinator
combinator = stream.next()
else:
combinator = ' '
consumed = len(stream.used)
next_selector = parse_simple_selector(stream)
if consumed == len(stream.used):
raise SelectorSyntaxError(
"Expected selector, got '%s'" % stream.peek())
result = CombinedSelector(result, combinator, next_selector)
return result
def parse_simple_selector(stream):
peek = stream.peek()
if peek != '*' and not isinstance(peek, Symbol):
element = namespace = '*'
else:
next = stream.next()
if next != '*' and not isinstance(next, Symbol):
raise SelectorSyntaxError(
"Expected symbol, got '%s'" % next)
if stream.peek() == '|':
namespace = next
stream.next()
element = stream.next()
if element != '*' and not isinstance(next, Symbol):
raise SelectorSyntaxError(
"Expected symbol, got '%s'" % next)
else:
namespace = '*'
element = next
result = Element(namespace, element)
has_hash = False
while 1:
peek = stream.peek()
if peek == '#':
if has_hash:
# You can't have two hashes
# (FIXME: is there some more general rule I'm missing?)
break
stream.next()
result = Hash(result, stream.next())
has_hash = True
continue
elif peek == '.':
stream.next()
result = Class(result, stream.next())
continue
elif peek == '[':
stream.next()
result = parse_attrib(result, stream)
next = stream.next()
if not next == ']':
raise SelectorSyntaxError(
"] expected, got '%s'" % next)
continue
elif peek == ':' or peek == '::':
type = stream.next()
ident = stream.next()
if not isinstance(ident, Symbol):
raise SelectorSyntaxError(
"Expected symbol, got '%s'" % ident)
if stream.peek() == '(':
stream.next()
peek = stream.peek()
if isinstance(peek, String):
selector = stream.next()
elif isinstance(peek, Symbol) and is_int(peek):
selector = int(stream.next())
else:
# FIXME: parse_simple_selector, or selector, or...?
selector = parse_simple_selector(stream)
next = stream.next()
if not next == ')':
raise SelectorSyntaxError(
"Expected ')', got '%s' and '%s'"
% (next, selector))
result = Function(result, type, ident, selector)
else:
result = Pseudo(result, type, ident)
continue
else:
if peek == ' ':
stream.next()
break
# FIXME: not sure what "negation" is
return result
def is_int(v):
try:
int(v)
except ValueError:
return False
else:
return True
def parse_attrib(selector, stream):
attrib = stream.next()
if stream.peek() == '|':
namespace = attrib
stream.next()
attrib = stream.next()
else:
namespace = '*'
if stream.peek() == ']':
return Attrib(selector, namespace, attrib, 'exists', None)
op = stream.next()
if not op in ('^=', '$=', '*=', '=', '~=', '|=', '!='):
raise SelectorSyntaxError(
"Operator expected, got '%s'" % op)
value = stream.next()
if not isinstance(value, (Symbol, String)):
raise SelectorSyntaxError(
"Expected string or symbol, got '%s'" % value)
return Attrib(selector, namespace, attrib, op, value)
def parse_series(s):
"""
Parses things like '1n+2', or 'an+b' generally, returning (a, b)
"""
if isinstance(s, Element):
s = s._format_element()
if not s or s == '*':
# Happens when there's nothing, which the CSS parser thinks of as *
return (0, 0)
if isinstance(s, int):
# Happens when you just get a number
return (0, s)
if s == 'odd':
return (2, 1)
elif s == 'even':
return (2, 0)
elif s == 'n':
return (1, 0)
if 'n' not in s:
# Just a b
return (0, int(s))
a, b = s.split('n', 1)
if not a:
a = 1
elif a == '-' or a == '+':
a = int(a+'1')
else:
a = int(a)
if not b:
b = 0
elif b == '-' or b == '+':
b = int(b+'1')
else:
b = int(b)
return (a, b)
############################################################
## Tokenizing
############################################################
_whitespace_re = re.compile(r'\s+', re.UNICODE)
_comment_re = re.compile(r'/\*.*?\*/', re.DOTALL)
_count_re = re.compile(r'[+-]?\d*n(?:[+-]\d+)?')
def tokenize(s):
pos = 0
s = _comment_re.sub('', s)
while 1:
match = _whitespace_re.match(s, pos=pos)
if match:
preceding_whitespace_pos = pos
pos = match.end()
else:
preceding_whitespace_pos = 0
if pos >= len(s):
return
match = _count_re.match(s, pos=pos)
if match and match.group() != 'n':
sym = s[pos:match.end()]
yield Symbol(sym, pos)
pos = match.end()
continue
c = s[pos]
c2 = s[pos:pos+2]
if c2 in ('~=', '|=', '^=', '$=', '*=', '::', '!='):
yield Token(c2, pos)
pos += 2
continue
if c in '>+~,.*=[]()|:#':
if c in '.#' and preceding_whitespace_pos > 0:
yield Token(' ', preceding_whitespace_pos)
yield Token(c, pos)
pos += 1
continue
if c == '"' or c == "'":
# Quoted string
old_pos = pos
sym, pos = tokenize_escaped_string(s, pos)
yield String(sym, old_pos)
continue
old_pos = pos
sym, pos = tokenize_symbol(s, pos)
yield Symbol(sym, old_pos)
continue
split_at_string_escapes = re.compile(r'(\\(?:%s))'
% '|'.join(['[A-Fa-f0-9]{1,6}(?:\r\n|\s)?',
'[^A-Fa-f0-9]'])).split
def unescape_string_literal(literal):
substrings = []
for substring in split_at_string_escapes(literal):
if not substring:
continue
elif '\\' in substring:
if substring[0] == '\\' and len(substring) > 1:
substring = substring[1:]
if substring[0] in '0123456789ABCDEFabcdef':
# int() correctly ignores the potentially trailing whitespace
substring = _unichr(int(substring, 16))
else:
raise SelectorSyntaxError(
"Invalid escape sequence %r in string %r"
% (substring.split('\\')[1], literal))
substrings.append(substring)
return ''.join(substrings)
def tokenize_escaped_string(s, pos):
quote = s[pos]
assert quote in ('"', "'")
pos = pos+1
start = pos
while 1:
next = s.find(quote, pos)
if next == -1:
raise SelectorSyntaxError(
"Expected closing %s for string in: %r"
% (quote, s[start:]))
result = s[start:next]
if result.endswith('\\'):
# next quote character is escaped
pos = next+1
continue
if '\\' in result:
result = unescape_string_literal(result)
return result, next+1
_illegal_symbol = re.compile(r'[^\w\\-]', re.UNICODE)
def tokenize_symbol(s, pos):
start = pos
match = _illegal_symbol.search(s, pos=pos)
if not match:
# Goes to end of s
return s[start:], len(s)
if match.start() == pos:
assert 0, (
"Unexpected symbol: %r at %s" % (s[pos], pos))
if not match:
result = s[start:]
pos = len(s)
else:
result = s[start:match.start()]
pos = match.start()
try:
result = result.encode('ASCII', 'backslashreplace').decode('unicode_escape')
except UnicodeDecodeError:
import sys
e = sys.exc_info()[1]
raise SelectorSyntaxError(
"Bad symbol %r: %s" % (result, e))
return result, pos
class TokenStream(object):
def __init__(self, tokens, source=None):
self.used = []
self.tokens = iter(tokens)
self.source = source
self.peeked = None
self._peeking = False
try:
self.next_token = self.tokens.next
except AttributeError:
# Python 3
self.next_token = self.tokens.__next__
def next(self):
if self._peeking:
self._peeking = False
self.used.append(self.peeked)
return self.peeked
else:
try:
next = self.next_token()
self.used.append(next)
return next
except StopIteration:
return None
def __iter__(self):
return iter(self.next, None)
def peek(self):
if not self._peeking:
try:
self.peeked = self.next_token()
except StopIteration:
return None
self._peeking = True
return self.peeked
|