# test formatting floats with large precision, that it doesn't overflow the buffer def test(num, num_str): if num == float('inf') or num == 0.0 and num_str != '0.0': # skip numbers that overflow or underflow the FP precision return for kind in ('e', 'f', 'g'): # check precision either side of the size of the buffer (32 bytes) for prec in range(23, 36, 2): fmt = '%.' + '%d' % prec + kind s = fmt % num check = abs(float(s) - num) if num > 1: check /= num if check > 1e-6: print('FAIL', num_str, fmt, s, len(s), check) # check pure zero test(0.0, '0.0') # check some powers of 10, making sure to include exponents with 3 digits for e in range(-8, 8): num = pow(10, e) test(num, '1e%d' % e)