Committed patch from Ryan May. It fixes error in loadtxt occurring when usecols is not None and dtypes are given.

I added the test suggested by Ryan.

2 files changed, 17 insertions, 2 deletions

diff --git a/numpy/lib/io.py b/numpy/lib/io.py
index 36723f1d8..b1ae192ec 100644
--- a/numpy/lib/io.py
+++ b/numpy/lib/io.py
@@ -292,8 +292,12 @@ def loadtxt(fname, dtype=float, comments='#', delimiter=None, converters=None,
     if converters is None:
         converters = {}
         if dtype.names is not None:
-            converterseq = [_getconv(dtype.fields[name][0]) \
-                            for name in dtype.names]
+            if usecols is None:
+                converterseq = [_getconv(dtype.fields[name][0]) \
+                                for name in dtype.names]
+            else:
+                converters.update([(col,_getconv(dtype.fields[name][0])) \
+                                    for col,name in zip(usecols, dtype.names)])
 
     for i,line in enumerate(fh):
         if i<skiprows: continue
diff --git a/numpy/lib/tests/test_io.py b/numpy/lib/tests/test_io.py
index e083a915b..6ece0222f 100644
--- a/numpy/lib/tests/test_io.py
+++ b/numpy/lib/tests/test_io.py
@@ -220,6 +220,17 @@ class TestLoadTxt(TestCase):
         c.seek(0)
         x = np.loadtxt(c, dtype=float, usecols=(1,2))
         assert_array_equal(x, a[:,1:])
+        
+        # Checking with dtypes defined converters. 
+        data = '''JOE 70.1 25.3
+                BOB 60.5 27.9
+                '''
+        c = StringIO.StringIO(data)
+        names = ['stid', 'temp']
+        dtypes = ['S4', 'f8']
+        arr = np.loadtxt(c, usecols=(0,2),dtype=zip(names,dtypes))
+        assert_equal(arr['stid'],  ["JOE",  "BOB"])
+        assert_equal(arr['temp'],  [25.3,  27.9])
 
 
 class Testfromregex(TestCase):