Hi,
I was trying to use loadtxt() today to read in some text data, and I had
a problem when I specified a dtype that only contained as many elements
as in columns in usecols. The example below shows the problem:
import numpy as np
import StringIO
data = '''STID RELH TAIR
JOE 70.1 25.3
BOB 60.5 27.9
'''
f = StringIO.StringIO(data)
names = ['stid', 'temp']
dtypes = ['S4', 'f8']
arr = np.loadtxt(f, usecols=(0,2),dtype=zip(names,dtypes), skiprows=1)
With current 1.1 (and SVN head), this yields:
IndexError Traceback (most recent call last)
/home/rmay/<ipython console> in <module>()
/usr/lib64/python2.5/site-packages/numpy/lib/io.pyc in loadtxt(fname,
dtype, comments, delimiter, converters, skiprows, usecols, unpack)
309 for j in xrange(len(vals))]
310 if usecols is not None:
--> 311 row = [converterseq[j](vals[j]) for j in usecols]
312 else:
313 row = [converterseq[j](val) for j,val in
enumerate(vals)]
IndexError: list index out of range
------------------------------------------
I've added a patch that checks for usecols, and if present, correctly
creates the converters dictionary to map each specified column with
converter for the corresponding field in the dtype. With the attached
patch, this works fine:
>arr
array([('JOE', 25.300000000000001), ('BOB', 27.899999999999999)],
dtype=[('stid', '|S4'), ('temp', '<f8')])
Comments? Can I get this in for 1.1.1?
Thanks,
Ryan
--
Ryan May
Graduate Research Assistant
School of Meteorology
University of Oklahoma
--- io.py.bak 2008-07-18 18:12:17.000000000 -0400
+++ io.py 2008-07-16 22:49:13.000000000 -0400
@@ -292,8 +292,13 @@
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
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