NF: function for upper/lower case file extensions

Restore ignoring case in file extensions by using an explicit function.

Author: matthew-brett

bin/parrec2nii

@@ -13,7 +13,7 @@ import nibabel.parrec as pr
 from nibabel.mriutils import calculate_dwell_time, MRIError
 import nibabel.nifti1 as nifti1
 from nibabel.filename_parser import splitext_addext
-from nibabel.volumeutils import array_to_file
+from nibabel.volumeutils import array_to_file, fname_ext_ul_case
 
 
 def _oneline(big_str):
@@ -140,6 +140,7 @@ def proc_file(infile, opts):
 
     # load the PAR header and data
     scaling = None if opts.scaling == 'off' else opts.scaling
+    infile = fname_ext_ul_case(infile)
     pr_img = pr.load(infile, opts.permit_truncated, scaling)
     pr_hdr = pr_img.header
     raw_data = pr_img.dataobj.get_unscaled()

nibabel/tests/test_utils.py

@@ -9,6 +9,8 @@
 ''' Test for volumeutils module '''
 from __future__ import division
 
+from os.path import exists
+
 from ..externals.six import BytesIO
 import tempfile
 import warnings
@@ -23,6 +25,7 @@
                            array_to_file,
                            allopen, # for backwards compatibility
                            BinOpener,
+                           fname_ext_ul_case,
                            calculate_scale,
                            can_cast,
                            write_zeros,
@@ -825,6 +828,31 @@ def test_BinOpener():
             assert_true(hasattr(fobj.fobj, 'compress'))
 
 
+def test_fname_ext_ul_case():
+    # Get filename ignoring the case of the filename extension
+    with InTemporaryDirectory():
+        with open('afile.TXT', 'wt') as fobj:
+            fobj.write('Interesting information')
+        # OSX usually has case-insensitive file systems; Windows also
+        os_cares_case = not exists('afile.txt')
+        with open('bfile.txt', 'wt') as fobj:
+            fobj.write('More interesting information')
+        # If there is no file, the case doesn't change
+        assert_equal(fname_ext_ul_case('nofile.txt'), 'nofile.txt')
+        assert_equal(fname_ext_ul_case('nofile.TXT'), 'nofile.TXT')
+        # If there is a file, accept upper or lower case for ext
+        if os_cares_case:
+            assert_equal(fname_ext_ul_case('afile.txt'), 'afile.TXT')
+            assert_equal(fname_ext_ul_case('bfile.TXT'), 'bfile.txt')
+        else:
+            assert_equal(fname_ext_ul_case('afile.txt'), 'afile.txt')
+            assert_equal(fname_ext_ul_case('bfile.TXT'), 'bfile.TXT')
+        assert_equal(fname_ext_ul_case('afile.TXT'), 'afile.TXT')
+        assert_equal(fname_ext_ul_case('bfile.txt'), 'bfile.txt')
+        # Not mixed case though
+        assert_equal(fname_ext_ul_case('afile.TxT'), 'afile.TxT')
+
+
 def test_allopen():
     # This import into volumeutils is for compatibility.  The code is the
     # ``openers`` module.

nibabel/volumeutils.py

@@ -15,6 +15,7 @@
 
 import numpy as np
 
+from os.path import exists, splitext
 from .casting import (shared_range, type_info, OK_FLOATS)
 from .openers import Opener
 
@@ -1514,6 +1515,38 @@ class BinOpener(Opener):
     compress_ext_map['.mgz'] = Opener.gz_def
 
 
+def fname_ext_ul_case(fname):
+    """ `fname` with ext changed to upper / lower case if file exists
+
+    Check for existence of `fname`.  If it does exist, return unmodified.  If
+    it doesn't, check for existence of `fname` with case changed from lower to
+    upper, or upper to lower.  Return this modified `fname` if it exists.
+    Otherwise return `fname` unmodified
+
+    Parameters
+    ----------
+    fname : str
+        filename.
+
+    Returns
+    -------
+    mod_fname : str
+        filename, maybe with extension of opposite case
+    """
+    if exists(fname):
+        return fname
+    froot, ext = splitext(fname)
+    if ext == ext.lower():
+        mod_fname = froot + ext.upper()
+        if exists(mod_fname):
+            return mod_fname
+    elif ext == ext.upper():
+        mod_fname = froot + ext.lower()
+        if exists(mod_fname):
+            return mod_fname
+    return fname
+
+
 def allopen(fileish, *args, **kwargs):
     """ Compatibility wrapper for old ``allopen`` function