python核心编程第十章练习

10-6

def safe_open(filename, mode):    try:        f = open(filename, mode)    except IOError:        f = None    return fsafe_open('10-6test.txt', 'w')safe_open('10-6test', 'w')

10-8

ef safe_input(prompt):    try:        i = raw_input(prompt)    except (EOFError, KeyboardInterrupt):        i = None    return i

10-9

import math, cmathdef safe_sqrt(num):    try:        sqr = math.sqrt(num)    except ValueError:        sqr = cmath.sqrt(num)    return sqrprint safe_sqrt(-1)print safe_sqrt(4)