1 files changed, 11 insertions, 7 deletions
diff --git a/silx/io/specfile.pyx b/silx/io/specfile.pyx
index 35f425b..39e8816 100644
--- a/silx/io/specfile.pyx
+++ b/silx/io/specfile.pyx
@@ -614,7 +614,7 @@ class Scan(object):
 
 def _string_to_char_star(string_):
     """Convert a string to ASCII encoded bytes when using python3"""
-    if sys.version.startswith("3") and not isinstance(string_, bytes):
+    if sys.version_info[0] >= 3 and not isinstance(string_, bytes):
         return bytes(string_, "ascii")
     return string_
 
@@ -629,15 +629,14 @@ def is_specfile(filename):
     """
     if not os.path.isfile(filename):
         return False
-    # test for presence of #S or #F in first two lines
-    f = open(filename)
-    for i, line in enumerate(f):
-        if line.startswith("#S ") or line.startswith("#F "):
-            f.close()
+    # test for presence of #S or #F in first 10 lines
+    with open(filename, "rb") as f:
+        chunk = f.read(2500)
+    for i, line in enumerate(chunk.split(b"\n")):
+        if line.startswith(b"#S ") or line.startswith(b"#F "):
             return True
         if i >= 10:
             break
-    f.close()
     return False
 
 
@@ -681,10 +680,15 @@ cdef class SpecFile(object):
 
     def __dealloc__(self):
         """Destructor: Calls SfClose(self.handle)"""
+        self.close()
+
+    def close(self):
+        """Close the file descriptor"""
         # handle is NULL if SfOpen failed
         if self.handle:
             if specfile_wrapper.SfClose(self.handle):
                 _logger.warning("Error while closing SpecFile")
+            self.handle = NULL
 
     def __len__(self):
         """Return the number of scans in the SpecFile