add more tests and examples on README

README.rst

@@ -55,6 +55,16 @@ Typical usage (as library):
     ...
 
 
+        **NOTE**
+        The official form of an ISBN is something like 'ISBN 979-10-90636-07-1'. However for most
+        applications only the numbers are important and you can always masked them if you need (see below).
+        This library works mainly with 'striped' ISBNs  (only numbers and X) like '0826497527'. You can
+        strip an isbn's like string by using ``canonical(isbnlike)`` (see below). You can
+        'mask' the isbn by using ``mask(isbn)``. So in the examples below, when you see 'isbn'
+        in the argument, it is a 'striped' ISBN, when the argument is an 'isbnlike' it is a string 
+        like 'ISBN 979-10-90636-07-1' or even something dirty like 'asdf 979-10-90636-07-1 bla bla'.
+
+
 Main Functions
 --------------
 
@@ -71,13 +81,13 @@ Main Functions
 	Transform isbn-10 to isbn-13.
 
 ``canonical(isbnlike)``
-	Keep only numbers and X. You will get strings like `9780321534965`.
+	Keep only numbers and X. You will get strings like `9780321534965` and `954430603X`.
 
 ``clean(isbnlike)``
 	Clean ISBN (only legal characters).
 
 ``notisbn(isbnlike, level='strict')``
-	Check with the goal to invalidate isbn-like.
+	Check with the goal to invalidate isbn-like. 
 
 ``get_isbnlike(text, level='normal')``
 	Extract all substrings that seem like ISBNs (very useful for scraping).
@@ -127,6 +137,7 @@ Main Functions
 ``ren(filename)``
 	Rename a file using metadata from an ISBN in his filename.
 
+See the file test_core_ and test_ext_ for **a lot of examples**.
 
 
 Install
@@ -278,3 +289,7 @@ Read ``isbnlib`` code in a very sctructured way at sourcegraph_ or 'the docs' at
 .. _readthedocs: http://bit.ly/ISBNLib_rtd
 
 .. _stackoverflow: http://stackoverflow.com/questions/tagged/isbnlib
+
+.. _test_core: https://github.com/xlcnd/isbnlib/blob/master/isbnlib/test/test_core.py
+
+.. _test_ext: https://github.com/xlcnd/isbnlib/blob/master/isbnlib/test/test_ext.py

isbnlib/_core.py

@@ -120,8 +120,10 @@ def to_isbn10(isbn13):
     """Transform isbn-13 to isbn-10."""
     isbn13 = canonical(isbn13)
     # Check prefix
-    if isbn13[:3] != ISBN13_PREFIX:
+    if isbn13[:3] != ISBN13_PREFIX:  
         return isbn13 if len(isbn13) == 10 and is_isbn10(isbn13) else None
+    if not is_isbn13(isbn13):
+        return None
     isbn10 = isbn13[3:]
     check = _check_digit10(isbn10[:-1])
     # Change check digit
@@ -133,6 +135,8 @@ def to_isbn13(isbn10):
     isbn10 = canonical(isbn10)
     if len(isbn10) == 13 and is_isbn13(isbn10):
         return isbn10
+    if not is_isbn10(isbn10):
+        return None
     isbn13 = ISBN13_PREFIX + isbn10[:-1]
     check = _check_digit13(isbn13)
     return isbn13 + check if check else None

isbnlib/test/test_core.py

@@ -38,13 +38,15 @@ def test__check_structure13():
 
 def test_is_isbn10():
     assert_equals(is_isbn10('0826497527'), True)
+    assert_equals(is_isbn10('isbn 0-8264-9752-7'), True)
     assert_equals(is_isbn10('0826497520'), False)
     assert_equals(is_isbn10('954430603X'), True)
 
 
 def test_is_isbn13():
     assert_equals(is_isbn13('9780826497529'), True)
     assert_equals(is_isbn13('9791090636071'), True)
+    assert_equals(is_isbn13('isbn 979-10-90636-07-1'), True)
     assert_equals(is_isbn13('9780826497520'), False)
     assert_equals(is_isbn13('9700000000000'), False)
     assert_equals(is_isbn13('9000000000000'), False)
@@ -54,18 +56,24 @@ def test_is_isbn13():
 def test_to_isbn10():
     assert_equals(to_isbn10('9780826497529'), '0826497527')
     assert_equals(to_isbn10('0826497527'), '0826497527')
-    assert_equals(to_isbn10('9780826497520'), '0826497527')  # ISBN13 not valid
+    assert_equals(to_isbn10('9780826497520'), None)     # ISBN13 not valid
     assert_equals(to_isbn10('9790826497529'), None)
     assert_equals(to_isbn10('97808264975X3'), None)
     assert_equals(to_isbn10('978-826497'), None)               # (bug #14)
+    assert_equals(to_isbn10('isbn 0-8264-9752-7'), '0826497527')
+    assert_equals(to_isbn10('isbn 979-10-90636-07-1'), None)
+    assert_equals(to_isbn10('isbn 978-0-8264-9752-9'), '0826497527')
+    assert_equals(to_isbn10('asdadv isbn 978-0-8264-9752-9'), '0826497527')
 
 
 def test_to_isbn13():
     assert_equals(to_isbn13('0826497527'), '9780826497529')
     assert_equals(to_isbn13('9780826497529'), '9780826497529')
-    assert_equals(to_isbn13('0826497520'), '9780826497529')  # ISBN10 not valid
+    assert_equals(to_isbn13('0826497520'), None)        # ISBN10 not valid
     assert_equals(to_isbn13('08X6497527'), None)
     assert_equals(to_isbn13('91-43-01019-9'), '9789143010190') # (bug #14)
+    assert_equals(to_isbn13('isbn 91-43-01019-9'), '9789143010190')
+    assert_equals(to_isbn13('asd isbn 979-10-90636-07-1 blabla'), '9791090636071')
 
 
 def test_clean():
@@ -122,7 +130,7 @@ def test_canonical():
     assert_equals(canonical('ISBN9780826497529'), '9780826497529')
     assert_equals(canonical('isbn9780826497529'), '9780826497529')
     assert_equals(canonical('isbn 0826497527'), '0826497527')
-    assert_equals(get_canonical_isbn('954430603x'), '954430603X')
+    assert_equals(canonical('954430603x'), '954430603X')
 
 
 def test_EAN13():