Steps To Reproduce

Download the file https://users.cecs.anu.edu.au/~bdm/data/5reg_20-32.pc and run the code:

file = open("5reg_20-32.pc")
list( graphs._read_planar_code(file) )

Expected Behavior

It is expected that we obtain a list of 6 graphs contained in 5reg_20-32.pc in Plantri format.

Actual Behavior

We get an error:

ValueError: 10 and 6 are not neighbors but 10 is in the list associated with 6

Deep down, the reason is that, since we opened the file in text mode, _read_planar_code starts screwing things up as soon as it encounters code 0x0A (encoding vertex number 10 in Plantri). However, apparent attempt to change the mode via open("5reg_20-32.pc", "rb") raises another error in line 1493:

AssertionError: Not a valid planar code header

Additional Information

Line 1493 should perform comparison to a binary string, that is, header == b'>>planar_code<<'. It will also ensure that the file is opened in binary mode, so an error message could be made a bit more general - like:

assert header == b'>>planar_code<<', 'Not a valid planar code header or file is not opened in binary mode'

Environment

• OS: Ubuntu 24.04.2 LTS
• Sage Version: 10.7.beta1

Checklist

• I have searched the existing issues for a bug report that matches the one I want to file, without success.
• I have read the documentation and troubleshoot guide