use context managers for open()

src/calibre/ebooks/lrf/html/convert_from.py

@@ -352,10 +352,9 @@ class HTMLConverter(object):
             if not os.path.exists(tdir):
                 os.makedirs(tdir)
             try:
-                dump = open(os.path.join(tdir, 'html2lrf-verbose.html'), 'wb')
-                dump.write(unicode_type(soup).encode('utf-8'))
-                self.log.info(_('Written preprocessed HTML to ')+dump.name)
-                dump.close()
+                with open(os.path.join(tdir, 'html2lrf-verbose.html'), 'wb') as f:
+                    f.write(unicode_type(soup).encode('utf-8'))
+                    self.log.info(_('Written preprocessed HTML to ')+f.name)
             except:
                 pass
 
@@ -375,7 +374,7 @@ class HTMLConverter(object):
 
         if not os.path.exists(path):
             path = path.replace('&', '%26')  # convertlit replaces & with %26 in file names
-        f = open(path, 'rb')
+        with open(path, 'rb') as f:
             raw = f.read()
         if self.pdftohtml:  # Bug in pdftohtml that causes it to output invalid UTF-8 files
             raw = raw.decode('utf-8', 'ignore')
@@ -383,7 +382,6 @@ class HTMLConverter(object):
             raw = raw.decode(self.encoding, 'ignore')
         else:
             raw = xml_to_unicode(raw, self.verbose)[0]
-        f.close()
         soup = self.preprocess(raw)
         self.log.info(_('\tConverting to BBeB...'))
         self.current_style = {}
@@ -1935,7 +1933,8 @@ def try_opf(path, options, logger):
 
     dirpath = os.path.dirname(os.path.abspath(opf))
     from calibre.ebooks.metadata.opf2 import OPF as OPF2
-    opf = OPF2(open(opf, 'rb'), dirpath)
+    with open(opf, 'rb') as f:
+        opf = OPF2(f, dirpath)
     try:
         title = opf.title
         if title and not getattr(options, 'title', None):

src/calibre/ebooks/lrf/pylrs/pylrf.py

@@ -687,9 +687,8 @@ class LrfWriter(object):
         self.tocObjId = obj.objId
 
     def setThumbnailFile(self, filename, encoding=None):
-        f = open(filename, "rb")
+        with open(filename, "rb") as f:
             self.thumbnailData = f.read()
-        f.close()
 
         if encoding is None:
             encoding = os.path.splitext(filename)[1][1:]

src/calibre/ebooks/lrf/pylrs/pylrs.py

@@ -2268,9 +2268,8 @@ class ImageStream(LrsObject, LrsContainer):
         self.encoding = encoding
 
     def toLrf(self, lrfWriter):
-        imageFile = open(self.filename, "rb")
-        imageData = imageFile.read()
-        imageFile.close()
+        with open(self.filename, "rb") as f:
+            imageData = f.read()
 
         isObj = LrfObject("ImageStream", self.objId)
         if self.comment is not None:

src/calibre/ebooks/metadata/extz.py

@@ -64,7 +64,8 @@ def set_metadata(stream, mi):
             raise Exception('no cover')
     except:
         try:
-            new_cdata = open(mi.cover, 'rb').read()
+            with open(mi.cover, 'rb') as f:
+                new_cdata = f.read()
         except:
             pass
     if new_cdata:

src/calibre/ebooks/metadata/meta.py

@@ -215,7 +215,8 @@ def opf_metadata(opfpath):
                 cpath = os.path.join(os.path.dirname(opfpath), opf.cover)
                 if os.access(cpath, os.R_OK):
                     fmt = cpath.rpartition('.')[-1]
-                    data = open(cpath, 'rb').read()
+                    with open(cpath, 'rb') as f:
+                        data = f.read()
                     mi.cover_data = (fmt, data)
             return mi
     except:

src/calibre/ebooks/metadata/mobi.py

@@ -443,7 +443,10 @@ class MetadataUpdater(object):
 
         if mi.cover_data[1] or mi.cover:
             try:
-                data =  mi.cover_data[1] if mi.cover_data[1] else open(mi.cover, 'rb').read()
+                data =  mi.cover_data[1]
+                if not data:
+                    with open(mi.cover, 'rb') as f:
+                        data = f.read()
             except:
                 pass
             else:

src/calibre/ebooks/metadata/toc.py

@@ -180,7 +180,8 @@ class TOC(list):
     def read_ncx_toc(self, toc, root=None):
         self.base_path = os.path.dirname(toc)
         if root is None:
-            raw  = xml_to_unicode(open(toc, 'rb').read(), assume_utf8=True,
+            with open(toc, 'rb') as f:
+                raw  = xml_to_unicode(f.read(), assume_utf8=True,
                         strip_encoding_pats=True)[0]
             root = etree.fromstring(raw, parser=etree.XMLParser(recover=True,
                 no_network=True))
@@ -234,7 +235,9 @@ class TOC(list):
 
     def read_html_toc(self, toc):
         self.base_path = os.path.dirname(toc)
-        for href, fragment, txt in parse_html_toc(lopen(toc, 'rb').read()):
+        with lopen(toc, 'rb') as f:
+            parsed_toc = parse_html_toc(f.read())
+        for href, fragment, txt in parsed_toc:
             add = True
             for i in self.flat():
                 if i.href == href and i.fragment == fragment: