#10198: fix duplicate header when writeframes() is called with an empty string.

Lib/wave.py

@@ -319,6 +319,7 @@ class Wave_write:
         self._nframeswritten = 0
         self._datawritten = 0
         self._datalength = 0
+        self._headerwritten = False
 
     def __del__(self):
         self.close()
@@ -449,7 +450,7 @@ class Wave_write:
     #
 
     def _ensure_header_written(self, datasize):
-        if not self._datawritten:
+        if not self._headerwritten:
             if not self._nchannels:
                 raise Error('# channels not specified')
             if not self._sampwidth:
@@ -459,6 +460,7 @@ class Wave_write:
             self._write_header(datasize)
 
     def _write_header(self, initlength):
+        assert not self._headerwritten
         self._file.write(b'RIFF')
         if not self._nframes:
             self._nframes = initlength // (self._nchannels * self._sampwidth)
@@ -472,8 +474,10 @@ class Wave_write:
             self._sampwidth * 8, 'data'))
         self._data_length_pos = self._file.tell()
         self._file.write(struct.pack('<l', self._datalength))
+        self._headerwritten = True
 
     def _patchheader(self):
+        assert self._headerwritten
         if self._datawritten == self._datalength:
             return
         curpos = self._file.tell()

Misc/NEWS

@@ -57,6 +57,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #10198: fix duplicate header written to wave files when writeframes()
+  is called without data.
+
 - Close file objects in modulefinder in a timely manner.
 
 - Close a io.TextIOWrapper object in email.parser in a timely manner.