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1"""Fixer for except statements with named exceptions.2 3The following cases will be converted:4 5- "except E, T:" where T is a name:6 7    except E as T:8 9- "except E, T:" where T is not a name, tuple or list:10 11        except E as t:12            T = t13 14    This is done because the target of an "except" clause must be a15    name.16 17- "except E, T:" where T is a tuple or list literal:18 19        except E as t:20            T = t.args21"""22# Author: Collin Winter23 24# Local imports25from .. import pytree26from ..pgen2 import token27from .. import fixer_base28from ..fixer_util import Assign, Attr, Name, is_tuple, is_list, syms29 30def find_excepts(nodes):31    for i, n in enumerate(nodes):32        if n.type == syms.except_clause:33            if n.children[0].value == 'except':34                yield (n, nodes[i+2])35 36class FixExcept(fixer_base.BaseFix):37    BM_compatible = True38 39    PATTERN = """40    try_stmt< 'try' ':' (simple_stmt | suite)41                  cleanup=(except_clause ':' (simple_stmt | suite))+42                  tail=(['except' ':' (simple_stmt | suite)]43                        ['else' ':' (simple_stmt | suite)]44                        ['finally' ':' (simple_stmt | suite)]) >45    """46 47    def transform(self, node, results):48        syms = self.syms49 50        tail = [n.clone() for n in results["tail"]]51 52        try_cleanup = [ch.clone() for ch in results["cleanup"]]53        for except_clause, e_suite in find_excepts(try_cleanup):54            if len(except_clause.children) == 4:55                (E, comma, N) = except_clause.children[1:4]56                comma.replace(Name("as", prefix=" "))57 58                if N.type != token.NAME:59                    # Generate a new N for the except clause60                    new_N = Name(self.new_name(), prefix=" ")61                    target = N.clone()62                    target.prefix = ""63                    N.replace(new_N)64                    new_N = new_N.clone()65 66                    # Insert "old_N = new_N" as the first statement in67                    #  the except body. This loop skips leading whitespace68                    #  and indents69                    #TODO(cwinter) suite-cleanup70                    suite_stmts = e_suite.children71                    for i, stmt in enumerate(suite_stmts):72                        if isinstance(stmt, pytree.Node):73                            break74 75                    # The assignment is different if old_N is a tuple or list76                    # In that case, the assignment is old_N = new_N.args77                    if is_tuple(N) or is_list(N):78                        assign = Assign(target, Attr(new_N, Name('args')))79                    else:80                        assign = Assign(target, new_N)81 82                    #TODO(cwinter) stopgap until children becomes a smart list83                    for child in reversed(suite_stmts[:i]):84                        e_suite.insert_child(0, child)85                    e_suite.insert_child(i, assign)86                elif N.prefix == "":87                    # No space after a comma is legal; no space after "as",88                    # not so much.89                    N.prefix = " "90 91        #TODO(cwinter) fix this when children becomes a smart list92        children = [c.clone() for c in node.children[:3]] + try_cleanup + tail93        return pytree.Node(node.type, children)94