From ce4ba897be5e4fc116f7cf805f38dec48cd5cfea Mon Sep 17 00:00:00 2001
From: Fred Drake <fdrake@acm.org>
Date: Tue, 18 Aug 1998 17:43:08 +0000
Subject: [PATCH] Raise the right exception (ValueError) for attempted I/O on
 closed StringIO objects; this makes the emulation of file objects a bit
 better, and the exceptions explain things a bit better.

---
 Lib/StringIO.py | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/Lib/StringIO.py b/Lib/StringIO.py
index dba38e42c0a..fc195b94af3 100644
--- a/Lib/StringIO.py
+++ b/Lib/StringIO.py
@@ -41,8 +41,12 @@ class StringIO:
 			self.closed = 1
 			del self.buf, self.pos
 	def isatty(self):
+		if self.closed:
+			raise ValueError, "I/O operation on closed file"
 		return 0
 	def seek(self, pos, mode = 0):
+		if self.closed:
+			raise ValueError, "I/O operation on closed file"
 		if self.buflist:
 			self.buf = self.buf + string.joinfields(self.buflist, '')
 			self.buflist = []
@@ -52,8 +56,12 @@ class StringIO:
 			pos = pos + self.len
 		self.pos = max(0, pos)
 	def tell(self):
+		if self.closed:
+			raise ValueError, "I/O operation on closed file"
 		return self.pos
 	def read(self, n = -1):
+		if self.closed:
+			raise ValueError, "I/O operation on closed file"
 		if self.buflist:
 			self.buf = self.buf + string.joinfields(self.buflist, '')
 			self.buflist = []
@@ -65,6 +73,8 @@ class StringIO:
 		self.pos = newpos
 		return r
 	def readline(self, length=None):
+		if self.closed:
+			raise ValueError, "I/O operation on closed file"
 		if self.buflist:
 			self.buf = self.buf + string.joinfields(self.buflist, '')
 			self.buflist = []
@@ -87,6 +97,8 @@ class StringIO:
 			line = self.readline()
 		return lines
 	def write(self, s):
+		if self.closed:
+			raise ValueError, "I/O operation on closed file"
 		if not s: return
 		if self.pos > self.len:
 			self.buflist.append('\0'*(self.pos - self.len))
@@ -105,7 +117,8 @@ class StringIO:
 	def writelines(self, list):
 		self.write(string.joinfields(list, ''))
 	def flush(self):
-		pass
+		if self.closed:
+			raise ValueError, "I/O operation on closed file"
 	def getvalue(self):
 		if self.buflist:
 			self.buf = self.buf + string.joinfields(self.buflist, '')