revamped `BufferedInput` class

buffered_input.py

class BufferedInput:
    def __init__(self):
        # the buffer holds the content that has be entered by the user but has not been read by into a variable yet
        self.buffer = ''

    def getc(self):
        self.fill_buffer()

        byte = self.buffer[0]
        self.buffer = self.buffer[1:]
        return byte

    def ungetc(self, s):
        # add the character at the beginning of the present buffer so that it can be read later
        self.buffer = s + self.buffer

    def getword(self):
        # the word will be read in this variable
        w = ''

        while True:
            # keep appending characters to w as long as no whitespace is encountered
            c = self.getc()
            if c not in {' ', '\t', '\n'} and w:
                w += c
            else:
                break

        if w:
            return w
        else:
            # In case, no word is entered and EOF is encountered, we raise this exception
            raise EOFError(“Input source exhausted.”)

    def getint(self):
        # skip whitespace
        c = ' '
        while c in {' ', '\t', '\n'}:
            c = self.getc()

        # get the sign for the number if any
        sign = c
        if sign not in {'-', '+'}:
            # if no sign is available, put the read character back into the buffer and use an empty character for the sign
            self.ungetc(sign)
            sign = ''

        # get the first digit of the number
        # if it is not a digit, raise an exception
        digit = self.getc()
        if ord(digit) not in range(ord('0'), ord('9') + 1):
            raise ValueError(“A number was expected.”)

        num = ''
        # keep getting a digit as long as no non-digit characters are encountered and append to num
        while digit.isdigit() and digit not in {' ', '\t', '\n'}:
            num += digit
            digit = self.getc()
        self.ungetc(digit)    # the last char read is a non-digit

        return int(num)

    def getfloat(self):
        # the value before the decimal point
        pre_dot_num = str(self.getint())

        # the value after the decimal point
        post_dot_num = ''

        # the decimal point itself
        # if the decimal point is not available, unread it
        dot = self.getc()
        if dot == '.':
            digit = self.getc()
            if ord(digit) not in range(ord('0'), ord('9') + 1):
                self.ungetc(digit)
                return float(pre_dot_num)
            
            while digit.isdigit() and digit not in {' ', '\t', '\n'}:
                post_dot_num += digit
                digit = self.getc()
            self.ungetc(digit)
        return float(pre_dot_num + dot + post_dot_num)

    def fill_buffer(self):
        if not self.buffer:
            self.buffer = input() + '\n'    # input strips the trailing new line, so we add it explicitly

    def empty_buffer(self):
        copy = self.buffer
        self.buffer = ''
        return copy