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# -*- coding: utf-8 -*-
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# Copyright (C) 2012-2013 Vinay Sajip.
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# Licensed to the Python Software Foundation under a contributor agreement.
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# See LICENSE.txt and CONTRIBUTORS.txt.
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"""Parser for the environment markers micro-language defined in PEP 345."""
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from .compat import python_implementation, string_types
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from .util import in_venv
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__all__ = ['interpret']
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class Evaluator(object):
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A limited evaluator for Python expressions.
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'eq': lambda x, y: x == y,
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'gt': lambda x, y: x > y,
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'gte': lambda x, y: x >= y,
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'in': lambda x, y: x in y,
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'lt': lambda x, y: x < y,
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'lte': lambda x, y: x <= y,
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'not': lambda x: not x,
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'noteq': lambda x, y: x != y,
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'notin': lambda x, y: x not in y,
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'sys.platform': sys.platform,
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'python_version': '%s.%s' % sys.version_info[:2],
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# parsing sys.platform is not reliable, but there is no other
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# way to get e.g. 2.7.2+, and the PEP is defined with sys.version
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'python_full_version': sys.version.split(' ', 1)[0],
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'platform.in_venv': str(in_venv()),
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'platform.version': platform.version(),
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'platform.machine': platform.machine(),
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'platform.python_implementation': platform.python_implementation(),
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def __init__(self, context=None):
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Initialise an instance.
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:param context: If specified, names are looked up in this mapping.
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self.context = context or {}
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def get_fragment(self, offset):
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Get the part of the source which is causing a problem.
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s = '%r' % (self.source[offset:offset + fragment_len])
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if offset + fragment_len < len(self.source):
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def get_handler(self, node_type):
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Get a handler for the specified AST node type.
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return getattr(self, 'do_%s' % node_type, None)
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def evaluate(self, node, filename=None):
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Evaluate a source string or node, using ``filename`` when
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if isinstance(node, string_types):
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kwargs = {'mode': 'eval'}
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kwargs['filename'] = filename
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node = ast.parse(node, **kwargs)
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except SyntaxError as e:
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s = self.get_fragment(e.offset)
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raise SyntaxError('syntax error %s' % s)
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node_type = node.__class__.__name__.lower()
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handler = self.get_handler(node_type)
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if self.source is None:
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s = '(source not available)'
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s = self.get_fragment(node.col_offset)
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raise SyntaxError("don't know how to evaluate %r %s" % (
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def get_attr_key(self, node):
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assert isinstance(node, ast.Attribute), 'attribute node expected'
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return '%s.%s' % (node.value.id, node.attr)
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def do_attribute(self, node):
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if not isinstance(node.value, ast.Name):
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key = self.get_attr_key(node)
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valid = key in self.context or key in self.allowed_values
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raise SyntaxError('invalid expression: %s' % key)
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if key in self.context:
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result = self.context[key]
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result = self.allowed_values[key]
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def do_boolop(self, node):
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result = self.evaluate(node.values[0])
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is_or = node.op.__class__ is ast.Or
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is_and = node.op.__class__ is ast.And
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assert is_or or is_and
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if (is_and and result) or (is_or and not result):
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for n in node.values[1:]:
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result = self.evaluate(n)
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if (is_or and result) or (is_and and not result):
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def do_compare(self, node):
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def sanity_check(lhsnode, rhsnode):
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if isinstance(lhsnode, ast.Str) and isinstance(rhsnode, ast.Str):
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elif (isinstance(lhsnode, ast.Attribute)
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and isinstance(rhsnode, ast.Attribute)):
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klhs = self.get_attr_key(lhsnode)
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krhs = self.get_attr_key(rhsnode)
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s = self.get_fragment(node.col_offset)
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raise SyntaxError('Invalid comparison: %s' % s)
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lhs = self.evaluate(lhsnode)
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for op, rhsnode in zip(node.ops, node.comparators):
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sanity_check(lhsnode, rhsnode)
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op = op.__class__.__name__.lower()
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if op not in self.operators:
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raise SyntaxError('unsupported operation: %r' % op)
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rhs = self.evaluate(rhsnode)
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result = self.operators[op](lhs, rhs)
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def do_expression(self, node):
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return self.evaluate(node.body)
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def do_name(self, node):
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if node.id in self.context:
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result = self.context[node.id]
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elif node.id in self.allowed_values:
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result = self.allowed_values[node.id]
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raise SyntaxError('invalid expression: %s' % node.id)
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def do_str(self, node):
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def interpret(marker, execution_context=None):
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Interpret a marker and return a result depending on environment.
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:param marker: The marker to interpret.
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:param execution_context: The context used for name lookup.
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:type execution_context: mapping
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return Evaluator(execution_context).evaluate(marker.strip())
added
removed
pip/vendor/distlib/markers.py
