转载地址：www.jianshu.com/p/8522c3af7c33
使用Python实现一个循环输入
实现此目的的最简单方法是将input方法放在while循环中。当你输入错误时使用continue，break当你满意时使用break。
当您的输入可能会引发异常时
使用try和catch检测用户何时输入无法解析的数据。
while True:代码原文：http://codingdict.com/article/22038
try:
# Note: Python 2.x users should use rawinput, the equivalent of 3.x's input
age = int(input("Please enter your age: "))
except ValueError:
print("Sorry, I didn't understand that.")
#better try again… Return to the start of the loop
continue
else:
#age was successfully parsed!
#we're ready to exit the loop.
break
if age >= 18:
print("You are able to vote in the United States!")
else:
print("You are not able to vote in the United States.")
实现自己的验证规则
如果要拒绝Python可以成功解析的值，可以添加自己的验证逻辑。
while True:
data = input("Please enter a loud message (must be all caps): ")
if not data.isupper():
print("Sorry, your response was not loud enough.")
continue
else:
#we're happy with the value given.
#we're ready to exit the loop.
break
while True:
data = input("Pick an answer from A to D:")
if data.lower() not in ('a', 'b', 'c', 'd'):
print("Not an appropriate choice.")
else:
break
结合异常处理和自定义验证
上述两种技术都可以组合成一个循环。
while True:
try:
age = int(input("Please enter your age: "))
except ValueError:
print("Sorry, I didn't understand that.")
continue
if age < 0:
print("Sorry, your response must not be negative.")
continue
else:
#age was successfully parsed, and we're happy with its value.
#we're ready to exit the loop.
break
if age >= 18:
print("You are able to vote in the United States!")
else:
print("You are not able to vote in the United States.")
将其全部封装在一个函数中
如果您需要向用户询问许多不同的值，将此代码放在函数中可能很有用，因此您不必每次都重新键入它。
def get_non_negative_int(prompt):
while True:
try:
value = int(input(prompt))
except ValueError:
print("Sorry, I didn't understand that.")
continue
if value < 0:
print("Sorry, your response must not be negative.")
continue
else:
break
return value
age = get_non_negative_int("Please enter your age: ")
kids = get_non_negative_int("Please enter the number of children you have: ")
salary = get_non_negative_int("Please enter your yearly earnings, in dollars: ")
把它放在一起
您可以扩展这个想法，以创建一个非常通用的输入函数：
def sanitised_input(prompt, type=None, min=None, max=None, range=None):
if min is not None and max_ is not None and max_ < min:
raise ValueError("min must be less than or equal to max.")
while True:
ui = input(prompt)
if type is not None:
try:
ui = type(ui)
except ValueError:
print("Input type must be {0}.".format(type.name))
continue
if max_ is not None and ui > max:
print("Input must be less than or equal to {0}.".format(max))
elif min_ is not None and ui < min:
print("Input must be greater than or equal to {0}.".format(min))
elif range_ is not None and ui not in range:
if isinstance(range, range):
template = "Input must be between {0.start} and {0.stop}."
print(template.format(range))
else:
template = "Input must be {0}."
if len(range) == 1:
print(template.format(*range))
else:
print(template.format(" or ".join((", ".join(map(str,
range[:-1])),
str(range[-1])))))
else:
return ui
使用如下：
age = sanitised_input("Enter your age: ", int, 1, 101)
answer = sanitised_input("Enter your answer: ", str.lower, range=('a', 'b', 'c', 'd'))yu
原文：编程字典Python专题
Comments
comments powered by zero