From d2bb18b28165ccc6e4678e8046abe6ea7c9677b3 Mon Sep 17 00:00:00 2001
From: Alexandre Vassalotti <alexandre@peadrop.com>
Date: Wed, 22 Jul 2009 03:07:33 +0000
Subject: Issue #6241: Better type checking for the arguments of io.StringIO.

---
 Lib/_pyio.py | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

(limited to 'Lib/_pyio.py')

diff --git a/Lib/_pyio.py b/Lib/_pyio.py
index bbf65bc0b1..5458f990b7 100644
--- a/Lib/_pyio.py
+++ b/Lib/_pyio.py
@@ -1924,8 +1924,10 @@ class StringIO(TextIOWrapper):
         # C version, even under Windows.
         if newline is None:
             self._writetranslate = False
-        if initial_value:
+        if initial_value is not None:
             if not isinstance(initial_value, str):
+                raise TypeError("initial_value must be str or None, not {0}"
+                                .format(type(initial_value).__name__))
                 initial_value = str(initial_value)
             self.write(initial_value)
             self.seek(0)
-- 
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