晋太元中,武陵人捕鱼为业。缘溪行,忘路之远近。忽逢桃花林,夹岸数百步,中无杂树,芳草鲜美,落英缤纷。渔人甚异之,复前行,欲穷其林。 林尽水源,便得一山,山有小口,仿佛若有光。便舍船,从口入。初极狭,才通人。复行数十步,豁然开朗。土地平旷,屋舍俨然,有良田、美池、桑竹之属。阡陌交通,鸡犬相闻。其中往来种作,男女衣着,悉如外人。黄发垂髫,并怡然自乐。 见渔人,乃大惊,问所从来。具答之。便要还家,设酒杀鸡作食。村中闻有此人,咸来问讯。自云先世避秦时乱,率妻子邑人来此绝境,不复出焉,遂与外人间隔。问今是何世,乃不知有汉,无论魏晋。此人一一为具言所闻,皆叹惋。余人各复延至其家,皆出酒食。停数日,辞去。此中人语云:“不足为外人道也。”(间隔 一作:隔绝) 既出,得其船,便扶向路,处处志之。及郡下,诣太守,说如此。太守即遣人随其往,寻向所志,遂迷,不复得路。 南阳刘子骥,高尚士也,闻之,欣然规往。未果,寻病终。后遂无问津者。
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# This file is dual licensed under the terms of the Apache License, Version
# 2.0, and the BSD License. See the LICENSE file in the root of this repository
# for complete details.
from __future__ import absolute_import, division, print_function
import operator
import os
import platform
import sys
from pip._vendor.pyparsing import (
ParseException, ParseResults, stringStart, stringEnd,
)
from pip._vendor.pyparsing import ZeroOrMore, Group, Forward, QuotedString
from pip._vendor.pyparsing import Literal as L # noqa
from ._compat import string_types
from .specifiers import Specifier, InvalidSpecifier
__all__ = [
"InvalidMarker", "UndefinedComparison", "UndefinedEnvironmentName",
"Marker", "default_environment",
]
class InvalidMarker(ValueError):
"""
An invalid marker was found, users should refer to PEP 508.
"""
class UndefinedComparison(ValueError):
"""
An invalid operation was attempted on a value that doesn't support it.
"""
class UndefinedEnvironmentName(ValueError):
"""
A name was attempted to be used that does not exist inside of the
environment.
"""
class Node(object):
def __init__(self, value):
self.value = value
def __str__(self):
return str(self.value)
def __repr__(self):
return "<{0}({1!r})>".format(self.__class__.__name__, str(self))
def serialize(self):
raise NotImplementedError
class Variable(Node):
def serialize(self):
return str(self)
class Value(Node):
def serialize(self):
return '"{0}"'.format(self)
class Op(Node):
def serialize(self):
return str(self)
VARIABLE = (
L("implementation_version") |
L("platform_python_implementation") |
L("implementation_name") |
L("python_full_version") |
L("platform_release") |
L("platform_version") |
L("platform_machine") |
L("platform_system") |
L("python_version") |
L("sys_platform") |
L("os_name") |
L("os.name") | # PEP-345
L("sys.platform") | # PEP-345
L("platform.version") | # PEP-345
L("platform.machine") | # PEP-345
L("platform.python_implementation") | # PEP-345
L("python_implementation") | # undocumented setuptools legacy
L("extra")
)
ALIASES = {
'os.name': 'os_name',
'sys.platform': 'sys_platform',
'platform.version': 'platform_version',
'platform.machine': 'platform_machine',
'platform.python_implementation': 'platform_python_implementation',
'python_implementation': 'platform_python_implementation'
}
VARIABLE.setParseAction(lambda s, l, t: Variable(ALIASES.get(t[0], t[0])))
VERSION_CMP = (
L("===") |
L("==") |
L(">=") |
L("<=") |
L("!=") |
L("~=") |
L(">") |
L("<")
)
MARKER_OP = VERSION_CMP | L("not in") | L("in")
MARKER_OP.setParseAction(lambda s, l, t: Op(t[0]))
MARKER_VALUE = QuotedString("'") | QuotedString('"')
MARKER_VALUE.setParseAction(lambda s, l, t: Value(t[0]))
BOOLOP = L("and") | L("or")
MARKER_VAR = VARIABLE | MARKER_VALUE
MARKER_ITEM = Group(MARKER_VAR + MARKER_OP + MARKER_VAR)
MARKER_ITEM.setParseAction(lambda s, l, t: tuple(t[0]))
LPAREN = L("(").suppress()
RPAREN = L(")").suppress()
MARKER_EXPR = Forward()
MARKER_ATOM = MARKER_ITEM | Group(LPAREN + MARKER_EXPR + RPAREN)
MARKER_EXPR << MARKER_ATOM + ZeroOrMore(BOOLOP + MARKER_EXPR)
MARKER = stringStart + MARKER_EXPR + stringEnd
def _coerce_parse_result(results):
if isinstance(results, ParseResults):
return [_coerce_parse_result(i) for i in results]
else:
return results
def _format_marker(marker, first=True):
assert isinstance(marker, (list, tuple, string_types))
# Sometimes we have a structure like [[...]] which is a single item list
# where the single item is itself it's own list. In that case we want skip
# the rest of this function so that we don't get extraneous () on the
# outside.
if (isinstance(marker, list) and len(marker) == 1 and
isinstance(marker[0], (list, tuple))):
return _format_marker(marker[0])
if isinstance(marker, list):
inner = (_format_marker(m, first=False) for m in marker)
if first:
return " ".join(inner)
else:
return "(" + " ".join(inner) + ")"
elif isinstance(marker, tuple):
return " ".join([m.serialize() for m in marker])
else:
return marker
_operators = {
"in": lambda lhs, rhs: lhs in rhs,
"not in": lambda lhs, rhs: lhs not in rhs,
"<": operator.lt,
"<=": operator.le,
"==": operator.eq,
"!=": operator.ne,
">=": operator.ge,
">": operator.gt,
}
def _eval_op(lhs, op, rhs):
try:
spec = Specifier("".join([op.serialize(), rhs]))
except InvalidSpecifier:
pass
else:
return spec.contains(lhs)
oper = _operators.get(op.serialize())
if oper is None:
raise UndefinedComparison(
"Undefined {0!r} on {1!r} and {2!r}.".format(op, lhs, rhs)
)
return oper(lhs, rhs)
_undefined = object()
def _get_env(environment, name):
value = environment.get(name, _undefined)
if value is _undefined:
raise UndefinedEnvironmentName(
"{0!r} does not exist in evaluation environment.".format(name)
)
return value
def _evaluate_markers(markers, environment):
groups = [[]]
for marker in markers:
assert isinstance(marker, (list, tuple, string_types))
if isinstance(marker, list):
groups[-1].append(_evaluate_markers(marker, environment))
elif isinstance(marker, tuple):
lhs, op, rhs = marker
if isinstance(lhs, Variable):
lhs_value = _get_env(environment, lhs.value)
rhs_value = rhs.value
else:
lhs_value = lhs.value
rhs_value = _get_env(environment, rhs.value)
groups[-1].append(_eval_op(lhs_value, op, rhs_value))
else:
assert marker in ["and", "or"]
if marker == "or":
groups.append([])
return any(all(item) for item in groups)
def format_full_version(info):
version = '{0.major}.{0.minor}.{0.micro}'.format(info)
kind = info.releaselevel
if kind != 'final':
version += kind[0] + str(info.serial)
return version
def default_environment():
if hasattr(sys, 'implementation'):
iver = format_full_version(sys.implementation.version)
implementation_name = sys.implementation.name
else:
iver = '0'
implementation_name = ''
return {
"implementation_name": implementation_name,
"implementation_version": iver,
"os_name": os.name,
"platform_machine": platform.machine(),
"platform_release": platform.release(),
"platform_system": platform.system(),
"platform_version": platform.version(),
"python_full_version": platform.python_version(),
"platform_python_implementation": platform.python_implementation(),
"python_version": platform.python_version()[:3],
"sys_platform": sys.platform,
}
class Marker(object):
def __init__(self, marker):
try:
self._markers = _coerce_parse_result(MARKER.parseString(marker))
except ParseException as e:
err_str = "Invalid marker: {0!r}, parse error at {1!r}".format(
marker, marker[e.loc:e.loc + 8])
raise InvalidMarker(err_str)
def __str__(self):
return _format_marker(self._markers)
def __repr__(self):
return "<Marker({0!r})>".format(str(self))
def evaluate(self, environment=None):
"""Evaluate a marker.
Return the boolean from evaluating the given marker against the
environment. environment is an optional argument to override all or
part of the determined environment.
The environment is determined from the current Python process.
"""
current_environment = default_environment()
if environment is not None:
current_environment.update(environment)
return _evaluate_markers(self._markers, current_environment)