New submission from Erik Wennstrom <ewenn...@indiana.edu>:
Sometimes, when the position on a text file object is right before a line break, the file object method .tell() returns a bizarre large number (18446744073709551621) instead of the correct position. The incorrect behavior occurs consistently for certain text files, but sometimes, a slight modification of the file will cause the behavior to revert to normal. I can get this behavior in both Python 3.7.2 and 3.6.5. I've seen it on two different Windows X machines. I've included two sample text files and a program that tests them both with the same code, which opens the file, reads 4 characters from the file, and then prints the result of the .tell() method. Both should print 4, but one of them prints 18446744073709551621. The only difference between the text files is that one of them has a single extra character before the last line break (which I should note is several lines away from the line where the weird behavior occurs). Frankly, I don't even have a sliver of an inkling of a notion as to how this error might happen. I encountered it in the middle of teaching an intro programming lecture where I was showing them how file object positions work with .read(). Brought the entire class to a screeching halt. ---------- components: Windows files: telltest.zip messages: 337148 nosy: erwenn, paul.moore, steve.dower, tim.golden, zach.ware priority: normal severity: normal status: open title: file object method .tell() sometimes returns large number when position is right before a line break type: behavior versions: Python 3.6, Python 3.7 Added file: https://bugs.python.org/file48186/telltest.zip _______________________________________ Python tracker <rep...@bugs.python.org> <https://bugs.python.org/issue36190> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
