使用curses在python中进行字符串切片

Question

Note. This question relates to code originally submitted to codereview

See oringinal link at https://codereview.stackexchange.com/questions/101011/mengenlehreuhr-in-python

So I have written a clock. Not just any clock, the purpose of this clock is to crack Kryptos section K4 .

Whilst the full source of the application is now on GitHub , the specific problem I am experiencing relates to the following method:

    def _update(self):
        self.window.erase()
        self.window.box()
        self.window.addstr(0, 1, str(self.index).zfill(2) + ' - ' + TimeDecipher.ciphertext[0:self.index])
        self.window.addstr(1, self.cipher_offset, TimeDecipher.ciphertext[0:self.index-1], self.color)
        self.window.addstr(
            1,
            (self.cipher_offset + self.index-1),
            TimeDecipher.ciphertext[self.index-1:self.index],
            self.highlight
        )
        self.window.addstr(1,
            (self.cipher_offset + self.index),
            TimeDecipher.ciphertext[self.index:],
            self.color
        )
        self.window.addstr(2, 1, ''.join(['-' for i in range(self.width - 2)]))
        for i, item in enumerate(self.lines):
            self.window.addstr((i + 3), 1, str(item))
        self.window.refresh()

The problem is described as follows.

When self.index < len(self.time_decipher.ciphertext) (97 characters), the highlighting works as anticipated.

OBKRUOX|O|GHULBSOLIFBBWFL...

However, when self.index == ~96 I see this:

|AR|OBKRUOX...

Basically the last 2 characters are cut from the end of the printed string and dropped at the start.

Please can someone explain why this is happening and what I can do to overcome this?

Answer 1

Problem solved - There was an issue with counting.

The method which set self.index was being passed that information from another method meaning it was always 1 behind the value required for splicing and reset to 0 when it reached 97 (the length of the string).

Because the slicing works from 1 to return, when it reached 96, the index was actually -1 and 97 was 0.

Updated Log::__add__ method to set index as:

    self.index = other.index if other.index > 0 else len(TimeDecipher.ciphertext) + other.index