Use exception handler target variables rather than sys.exc_info()

In Python 3, saving the exception object manually will create a reference
cycle via the traceback attribute. Using the exception handler method means
the variable is automatically deleted, avoiding the reference cycle.

Author: Martin Panter

scripts/runxlrd.py

@@ -89,9 +89,8 @@ def get_row_data(bk, sh, rowx, colrange):
             if cty == xlrd.XL_CELL_DATE:
                 try:
                     showval = xlrd.xldate_as_tuple(cval, dmode)
-                except xlrd.XLDateError:
-                    e1, e2 = sys.exc_info()[:2]
-                    showval = "%s:%s" % (e1.__name__, e2)
+                except xlrd.XLDateError as e:
+                    showval = "%s:%s" % (type(e).__name__, e)
                     cty = xlrd.XL_CELL_ERROR
             elif cty == xlrd.XL_CELL_ERROR:
                 showval = xlrd.error_text_from_code.get(cval, '<Unknown error code 0x%02x>' % cval)
@@ -335,17 +334,15 @@ def main(cmd_args):
                     t1 = time.time()
                     if not options.suppress_timing:
                         print("Open took %.2f seconds" % (t1-t0,))
-                except xlrd.XLRDError:
-                    e0, e1 = sys.exc_info()[:2]
-                    print("*** Open failed: %s: %s" % (e0.__name__, e1))
+                except xlrd.XLRDError as e:
+                    print("*** Open failed: %s: %s" % (type(e).__name__, e))
                     continue
                 except KeyboardInterrupt:
                     print("*** KeyboardInterrupt ***")
                     traceback.print_exc(file=sys.stdout)
                     sys.exit(1)
-                except:
-                    e0, e1 = sys.exc_info()[:2]
-                    print("*** Open failed: %s: %s" % (e0.__name__, e1))
+                except BaseException as e:
+                    print("*** Open failed: %s: %s" % (type(e).__name__, e))
                     traceback.print_exc(file=sys.stdout)
                     continue
                 t0 = time.time()

xlrd/book.py

@@ -773,11 +773,10 @@ def derive_encoding(self):
             # we're well & truly stuffed -- let the punter know ASAP.
             try:
                 _unused = unicode(b'trial', self.encoding)
-            except:
-                ei = sys.exc_info()[:2]
+            except BaseException as e:
                 fprintf(self.logfile,
                     "ERROR *** codepage %r -> encoding %r -> %s: %s\n",
-                    self.codepage, self.encoding, ei[0].__name__.split(".")[-1], ei[1])
+                    self.codepage, self.encoding, type(e).__name__.split(".")[-1], e)
                 raise
         if self.raw_user_name:
             strg = unpack_string(self.user_name, 0, self.encoding, lenlen=1)

xlrd/examples/xlrdnameAPIdemo.py

@@ -77,9 +77,8 @@ def showable_cell_value(celltype, cellvalue, datemode):
     if celltype == xlrd.XL_CELL_DATE:
         try:
             showval = xlrd.xldate_as_tuple(cellvalue, datemode)
-        except xlrd.XLDateError:
-            e1, e2 = sys.exc_info()[:2]
-            showval = "%s:%s" % (e1.__name__, e2)
+        except xlrd.XLDateError as e:
+            showval = "%s:%s" % (type(e).__name__, e)
     elif celltype == xlrd.XL_CELL_ERROR:
         showval = xlrd.error_text_from_code.get(
             cellvalue, '<Unknown error code 0x%02x>' % cellvalue)