Ignore unused converters in `loadtxt`.

2 files changed, 16 insertions, 1 deletions

diff --git a/numpy/lib/io.py b/numpy/lib/io.py
index 93c955942..caa790809 100644
--- a/numpy/lib/io.py
+++ b/numpy/lib/io.py
@@ -378,7 +378,11 @@ def loadtxt(fname, dtype=float, comments='#', delimiter=None, converters=None,
     # By preference, use the converters specified by the user
     for i, conv in (user_converters or {}).iteritems():
         if usecols:
-            i = usecols.index(i)
+            try:
+                i = usecols.index(i)
+            except ValueError:
+                # Unused converter specified
+                continue
         converters[i] = conv
 
     # Parse each line, including the first
diff --git a/numpy/lib/tests/test_io.py b/numpy/lib/tests/test_io.py
index 9cccbe041..d257b5423 100644
--- a/numpy/lib/tests/test_io.py
+++ b/numpy/lib/tests/test_io.py
@@ -258,6 +258,17 @@ class TestLoadTxt(TestCase):
         c = StringIO.StringIO()
         assert_raises(IOError, np.loadtxt, c)
 
+    def test_unused_converter(self):
+        c = StringIO.StringIO()
+        c.writelines(['1 21\n', '3 42\n'])
+        c.seek(0)
+        data = np.loadtxt(c, usecols=(1,), converters={0: lambda s: int(s, 16)})
+        assert_array_equal(data, [21, 42])
+
+        c.seek(0)
+        data = np.loadtxt(c, usecols=(1,), converters={1: lambda s: int(s, 16)})
+        assert_array_equal(data, [33, 66])
+
 class Testfromregex(TestCase):
     def test_record(self):
         c = StringIO.StringIO()