Python基础学习（一）

#Default Argument Values & in keyword

def ask_ok(prompt, retres=4, reminder=‘please try again!‘):    while True:        ok = input(prompt)        if ok in (‘y‘, ‘yes‘, ‘ye‘):            return True        if ok in (‘n‘, ‘no‘, ‘nop‘, ‘nope‘):            return False        if retres < 0:            print("err")            return ValueError(‘invalid user response‘)        print(reminder)

#All branches are normalask_ok(‘‘, -5, ‘a‘)#The last branch is wrongask_ok(‘‘, ‘-5‘, ‘a‘)

函数的默认参数学习和in关键字学习。

ask_ok(‘‘, ‘-5‘, ‘a‘)由于参数类型不匹配，提示错误信息如下：

D:\Python3.6.1\python.exe F:/python_workspace/tutorial/TestFunction.py
aaaa
Traceback (most recent call last):
File "F:/python_workspace/tutorial/TestFunction.py", line 18, in <module>
ask_ok(‘‘, ‘-5‘, ‘a‘)
File "F:/python_workspace/tutorial/TestFunction.py", line 11, in ask_ok
if retres < 0:
TypeError: ‘<‘ not supported between instances of ‘str‘ and ‘int‘

Process finished with exit code 1