Improvement on the invalid inputs

pyexcel_xls/__init__.py

@@ -111,7 +111,11 @@ class XLBook(BookReader):
         """Return iterable sheet array"""
         
         if self.sheet_name is not None:
-            return [self.native_book.sheet_by_name(self.sheet_name)]
+            try:
+                sheet = self.native_book.sheet_by_name(self.sheet_name)
+                return [sheet]
+            except xlrd.XLRDError:
+                raise ValueError("%s cannot be found" % self.sheet_name)
         elif self.sheet_index is not None:
             return [self.native_book.sheet_by_index(self.sheet_index)]
         else:

tests/test_mutliple_sheets.py

@@ -2,6 +2,7 @@ from base import PyexcelMultipleSheetBase
 import pyexcel
 import os
 from pyexcel.ext import xls
+from nose.tools import raises
 import sys
 
 if sys.version_info[0] == 2 and sys.version_info[1] < 7:
@@ -56,9 +57,17 @@ class TestAddBooks:
         assert b1['Sheet1'].to_array() == self.content['Sheet1']
 
     def test_load_a_single_sheet2(self):
-        b1 = pyexcel.load_book(self.testfile, sheet_index=0)
+        b1 = pyexcel.load_book(self.testfile, sheet_index=2)
         assert len(b1.sheet_names()) == 1
-        assert b1['Sheet1'].to_array() == self.content['Sheet1']
+        assert b1['Sheet3'].to_array() == self.content['Sheet3']
+
+    @raises(IndexError)
+    def test_load_a_single_sheet3(self):
+        pyexcel.load_book(self.testfile, sheet_index=10000)
+        
+    @raises(ValueError)
+    def test_load_a_single_sheet4(self):
+        pyexcel.load_book(self.testfile, sheet_name="Not exist")
 
     def test_delete_sheets(self):
         b1 = pyexcel.load_book(self.testfile)