[Python-bugs-list] [ python-Bugs-645594 ] for lin in file: file.tell() tells wrong

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Bugs item #645594, was opened at 2002-11-29 12:13
You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=105470&aid=645594&group_id=5470

Category: Python Library
Group: Python 2.2.2
Status: Open
Resolution: None
Priority: 5
Submitted By: Dmitry Vasiliev (hdima)
Assigned to: Nobody/Anonymous (nobody)
Summary: for lin in file: file.tell() tells wrong

Initial Comment:
Consider following piece of code:

f = file("test.txt", "rb")
pos = f.tell()
for line in f:
	print "%u: '%s'" % (pos, line)
	pos = f.tell()

During the code execution we have following result:

0 'Line 1'
63 'Line 2'
63 'Line 3'
...
63 'Line 9'

However, following piece of code works fine:

f = file("test.txt", "rb")
while True:
	pos = f.tell()
	line = f.readline()
	if line == "":
		break
	print "%u: '%s'" % (pos, line)

It prints:

0 'Line 1'
7 'Line 2'
14 'Line 3'
...
56 'Line 9'

It seems a file iterator makes file.tell() to tell
positions of some internal blocks used by the iterator.

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https://sourceforge.net/tracker/?func=detail&atid=105470&aid=645594&group_id=5470