All names have been removed to protect the guilty :-)
In an earlier post, I read a piece of code:
l1 = [1, 2, 3] l2 = [1, 2, 3] l1 == l2
True
I immediately gave a double-take: 11 equals 12? What gives? Can you re-bind literals in Python???
>>> 11 = [1, 2, 3] SyntaxError: can't assign to literal
And then it hit me. That wasn't eleven and twelve, the variable names were lowercase L with the digits one and two appended.
Imagine running a long piece of code on some test data and finding an off-by-one bug which you think is on the line "myvalue = something + l1". You change the eleven to 12 and now the code works on your test data but not for anything else.
If you have access to a syntax-aware editor, it will help avoid such problems, but better to avoid them in the first place. You might be reading code printed in black and white on dead tree one day.
Lesson the first: remember that in many fonts, zero and capital O are identical, as are lowercase L and 1 and sometimes even uppercase I. Avoid using names which can be easily confused for literals or for each other.
What are some of other people's favourite tips for avoiding bugs in the first place, as opposed to finding them once you know they are there?
-- Steven
-- http://mail.python.org/mailman/listinfo/python-list
