Python parser.expr() Examples

def decorator(self, nodelist):
        # '@' dotted_name [ '(' [arglist] ')' ]
        assert len(nodelist) in (3, 5, 6)
        assert nodelist[0][0] == token.AT
        assert nodelist[-1][0] == token.NEWLINE

        assert nodelist[1][0] == symbol.dotted_name
        funcname = self.decorator_name(nodelist[1][1:])

        if len(nodelist) > 3:
            assert nodelist[2][0] == token.LPAR
            expr = self.com_call_function(funcname, nodelist[3])
        else:
            expr = funcname

        return expr 

def decorator(self, nodelist):
        # '@' dotted_name [ '(' [arglist] ')' ]
        assert len(nodelist) in (3, 5, 6)
        assert nodelist[0][0] == token.AT
        assert nodelist[-1][0] == token.NEWLINE

        assert nodelist[1][0] == symbol.dotted_name
        funcname = self.decorator_name(nodelist[1][1:])

        if len(nodelist) > 3:
            assert nodelist[2][0] == token.LPAR
            expr = self.com_call_function(funcname, nodelist[3])
        else:
            expr = funcname

        return expr 

def __new__(cls,
                name,
                expr,
                replace = False):
        # code
        efound = expr in [Variable.variables[key].expr for key in Variable.variables]
        if efound:
            key = [key for key in Variable.variables if expr in Variable.variables[key].expr]
            logger.info("Expression '%s' already exists for key %s", expr, key)
            return
        else:
            if replace or not name in Variable.variables:
                if not valid_name(name):
                    logger.info("Invalid variable key: %s", name)
                    return
                try:
                    result = parser.expr(expr)
                except:
                    logger.info("Invalid expression: %s", expr)
                    return
                return super(Variable, cls).__new__(cls)
            else:
                logger.info("Key %s already exists", name)

    # function __init__ 

def build_atom(expr_string):
    """ Build an ast for an atom from the given expr string.

        If expr_string is not a string, it is converted to a string
        before parsing to an ast_tuple.
    """
    # the [1][1] indexing below starts atoms at the third level
    # deep in the resulting parse tree.  parser.expr will return
    # a tree rooted with eval_input -> test_list -> test ...
    # I'm considering test to be the root of atom symbols.
    # It might be a better idea to move down a little in the
    # parse tree. Any benefits? Right now, this works fine.
    if isinstance(expr_string, str):
        ast = parser.expr(expr_string).totuple()[1][1]
    else:
        ast = parser.expr(repr(expr_string)).totuple()[1][1]
    return ast 

def decorator(self, nodelist):
        # '@' dotted_name [ '(' [arglist] ')' ]
        assert len(nodelist) in (3, 5, 6)
        assert nodelist[0][0] == token.AT
        assert nodelist[-1][0] == token.NEWLINE

        assert nodelist[1][0] == symbol.dotted_name
        funcname = self.decorator_name(nodelist[1][1:])

        if len(nodelist) > 3:
            assert nodelist[2][0] == token.LPAR
            expr = self.com_call_function(funcname, nodelist[3])
        else:
            expr = funcname

        return expr 

def test_compile_expr(self):
        st = parser.expr('2 + 3')
        code = parser.compilest(st)
        self.assertEqual(eval(code), 5) 

def check_expr(self, s):
        self.roundtrip(parser.expr, s) 

def evaluate_marker(cls, text, extra=None):
        """
        Evaluate a PEP 426 environment marker on CPython 2.4+.
        Return a boolean indicating the marker result in this environment.
        Raise SyntaxError if marker is invalid.

        This implementation uses the 'parser' module, which is not implemented
        on
        Jython and has been superseded by the 'ast' module in Python 2.6 and
        later.
        """
        return cls.interpret(parser.expr(text).totuple(1)[1]) 

def evaluate_marker(cls, text, extra=None):
        """
        Evaluate a PEP 426 environment marker on CPython 2.4+.
        Return a boolean indicating the marker result in this environment.
        Raise SyntaxError if marker is invalid.

        This implementation uses the 'parser' module, which is not implemented
        on
        Jython and has been superseded by the 'ast' module in Python 2.6 and
        later.
        """
        return cls.interpret(parser.expr(text).totuple(1)[1]) 

def com_list_comprehension(self, expr, node):
        return self.com_comprehension(expr, None, node, 'list') 

def allvars(expr):
    r"""Get the list of valid names in the expression.

    Parameters
    ----------
    expr : str
        A valid expression conforming to the Variable Definition Language.

    Returns
    -------
    vlist : list
        List of valid variable names.

    """
    regex = re.compile('\w+')
    items = regex.findall(expr)
    vlist = []
    for item in items:
        if valid_name(item):
            vlist.append(item)
    return vlist


#
# Function vtree
# 

def evaluate_marker(cls, text, extra=None):
        """
        Evaluate a PEP 426 environment marker on CPython 2.4+.
        Return a boolean indicating the marker result in this environment.
        Raise SyntaxError if marker is invalid.

        This implementation uses the 'parser' module, which is not implemented
        on
        Jython and has been superseded by the 'ast' module in Python 2.6 and
        later.
        """
        return cls.interpret(parser.expr(text).totuple(1)[1]) 

def __str__(self):
        return self.expr


#
# Function vparse
# 

def __init__(self,
                 name,
                 expr,
                 replace = False):
        # code
        self.name = name;
        self.expr = expr;
        # add key with expression
        Variable.variables[name] = self
            
    # function __str__ 

def evaluate_marker(cls, text, extra=None):
        """
        Evaluate a PEP 426 environment marker on CPython 2.4+.
        Return a boolean indicating the marker result in this environment.
        Raise SyntaxError if marker is invalid.

        This implementation uses the 'parser' module, which is not implemented
        on
        Jython and has been superseded by the 'ast' module in Python 2.6 and
        later.
        """
        return cls.interpret(parser.expr(text).totuple(1)[1]) 

def test_issue_9011(self):
        # Issue 9011: compilation of an unary minus expression changed
        # the meaning of the ST, so that a second compilation produced
        # incorrect results.
        st = parser.expr('-3')
        code1 = parser.compilest(st)
        self.assertEqual(eval(code1), -3)
        code2 = parser.compilest(st)
        self.assertEqual(eval(code2), -3) 

def test_compile_expr(self):
        st = parser.expr('2 + 3')
        code = parser.compilest(st)
        self.assertEqual(eval(code), 5) 

def evaluate_marker(cls, text, extra=None):
        """
        Evaluate a PEP 426 environment marker on CPython 2.4+.
        Return a boolean indicating the marker result in this environment.
        Raise SyntaxError if marker is invalid.

        This implementation uses the 'parser' module, which is not implemented
        on
        Jython and has been superseded by the 'ast' module in Python 2.6 and
        later.
        """
        return cls.interpret(parser.expr(text).totuple(1)[1]) 

def check_expr(self, s):
        self.roundtrip(parser.expr, s) 

def com_dictorsetmaker(self, nodelist):
        # dictorsetmaker: ( (test ':' test (comp_for | (',' test ':' test)* [','])) |
        #                   (test (comp_for | (',' test)* [','])) )
        assert nodelist[0] == symbol.dictorsetmaker
        nodelist = nodelist[1:]
        if len(nodelist) == 1 or nodelist[1][0] == token.COMMA:
            # set literal
            items = []
            for i in range(0, len(nodelist), 2):
                items.append(self.com_node(nodelist[i]))
            return Set(items, lineno=items[0].lineno)
        elif nodelist[1][0] == symbol.comp_for:
            # set comprehension
            expr = self.com_node(nodelist[0])
            return self.com_comprehension(expr, None, nodelist[1], 'set')
        elif len(nodelist) > 3 and nodelist[3][0] == symbol.comp_for:
            # dict comprehension
            assert nodelist[1][0] == token.COLON
            key = self.com_node(nodelist[0])
            value = self.com_node(nodelist[2])
            return self.com_comprehension(key, value, nodelist[3], 'dict')
        else:
            # dict literal
            items = []
            for i in range(0, len(nodelist), 4):
                items.append((self.com_node(nodelist[i]),
                              self.com_node(nodelist[i+2])))
            return Dict(items, lineno=items[0][0].lineno) 

def check_expr(self, s):
        self.roundtrip(parser.expr, s) 

def com_with_item(self, nodelist, body, lineno):
        # with_item: test ['as' expr]
        if len(nodelist) == 4:
            var = self.com_assign(nodelist[3], OP_ASSIGN)
        else:
            var = None
        expr = self.com_node(nodelist[1])
        return With(expr, var, body, lineno=lineno) 

def com_try_except_finally(self, nodelist):
        # ('try' ':' suite
        #  ((except_clause ':' suite)+ ['else' ':' suite] ['finally' ':' suite]
        #   | 'finally' ':' suite))

        if nodelist[3][0] == token.NAME:
            # first clause is a finally clause: only try-finally
            return TryFinally(self.com_node(nodelist[2]),
                              self.com_node(nodelist[5]),
                              lineno=nodelist[0][2])

        #tryexcept:  [TryNode, [except_clauses], elseNode)]
        clauses = []
        elseNode = None
        finallyNode = None
        for i in range(3, len(nodelist), 3):
            node = nodelist[i]
            if node[0] == symbol.except_clause:
                # except_clause: 'except' [expr [(',' | 'as') expr]] */
                if len(node) > 2:
                    expr1 = self.com_node(node[2])
                    if len(node) > 4:
                        expr2 = self.com_assign(node[4], OP_ASSIGN)
                    else:
                        expr2 = None
                else:
                    expr1 = expr2 = None
                clauses.append((expr1, expr2, self.com_node(nodelist[i+2])))

            if node[0] == token.NAME:
                if node[1] == 'else':
                    elseNode = self.com_node(nodelist[i+2])
                elif node[1] == 'finally':
                    finallyNode = self.com_node(nodelist[i+2])
        try_except = TryExcept(self.com_node(nodelist[2]), clauses, elseNode,
                               lineno=nodelist[0][2])
        if finallyNode:
            return TryFinally(try_except, finallyNode, lineno=nodelist[0][2])
        else:
            return try_except 

def expr(self, nodelist):
        # xor_expr ('|' xor_expr)*
        return self.com_binary(Bitor, nodelist) 

def comparison(self, nodelist):
        # comparison: expr (comp_op expr)*
        node = self.com_node(nodelist[0])
        if len(nodelist) == 1:
            return node

        results = []
        for i in range(2, len(nodelist), 2):
            nl = nodelist[i-1]

            # comp_op: '<' | '>' | '=' | '>=' | '<=' | '<>' | '!=' | '=='
            #          | 'in' | 'not' 'in' | 'is' | 'is' 'not'
            n = nl[1]
            if n[0] == token.NAME:
                type = n[1]
                if len(nl) == 3:
                    if type == 'not':
                        type = 'not in'
                    else:
                        type = 'is not'
            else:
                type = _cmp_types[n[0]]

            lineno = nl[1][2]
            results.append((type, self.com_node(nodelist[i])))

        # we need a special "compare" node so that we can distinguish
        #   3 < x < 5   from    (3 < x) < 5
        # the two have very different semantics and results (note that the
        # latter form is always true)

        return Compare(node, results, lineno=lineno) 

def exec_stmt(self, nodelist):
        # exec_stmt: 'exec' expr ['in' expr [',' expr]]
        expr1 = self.com_node(nodelist[1])
        if len(nodelist) >= 4:
            expr2 = self.com_node(nodelist[3])
            if len(nodelist) >= 6:
                expr3 = self.com_node(nodelist[5])
            else:
                expr3 = None
        else:
            expr2 = expr3 = None

        return Exec(expr1, expr2, expr3, lineno=nodelist[0][2]) 

def yield_stmt(self, nodelist):
        expr = self.com_node(nodelist[0])
        return Discard(expr, lineno=expr.lineno) 

def parseexpr(self, text):
        """Return a modified parse tree for the given expression text."""
        return self.transform(parser.expr(text)) 

def eval_string_and_vars(eq_string, vars_in):
    for var in vars_in:
        eq_string = eq_string.replace(var, str(vars_in[var]))
    eq = parser.expr(eq_string).compile()
    return eval(eq) 

def test_issue_9011(self):
        # Issue 9011: compilation of an unary minus expression changed
        # the meaning of the ST, so that a second compilation produced
        # incorrect results.
        st = parser.expr('-3')
        code1 = parser.compilest(st)
        self.assertEqual(eval(code1), -3)
        code2 = parser.compilest(st)
        self.assertEqual(eval(code2), -3)