如何在python中无限循环这个程序

将其包裹在while循环中：

repeat = "yes"
while repeat.lower().strip() == 'yes':
    a,b=input("Enter two numbers (sperated by a comma): ")
    operator=raw_input("Do you want to add, subtract, multiply, or divide? ")
    if operator=="divide":
        print "Your answer is", a / b
    if operator=="multiply":
        print "Your answer is", a * b
    if operator=="add":
        print "Your answer is", a + b
    if operator=="subtract":
        print "Your answer is", a - b    
    repeat=raw_input("Do you want to perform another calculation(yes or no)? ")

只要答案是"yes"（不区分大小写），此操作就会循环。初始的"repeat"是为了保证循环至少运行一次。

顺便说一下，你可以把你的if测试变成一个dict:

import operator
ops = {'divide': operator.div,
       'multiply': operator.mul,
       'add': operator.add,
       'subtract': operator.sub}
repeat = "yes"
while repeat.lower().strip() == 'yes':
    a,b=input("Enter two numbers (sperated by a comma): ")
    operator=raw_input("Do you want to add, subtract, multiply, or divide? ").lower().strip()
    if operator not in ops:
        print 'Invalid operator:', operator
        continue
    print "Your answer is", ops[operator](a,b)
    repeat=raw_input("Do you want to perform another calculation(yes or no)? ")

while True:
    a,b=input("Enter two numbers (sperated by a comma): ")
    operator=raw_input("Do you want to add, subtract, multiply, or divide? ")
    if operator=="divide":
        print "Your answer is", a / b
    if operator=="multiply":
        print "Your answer is", a * b
    if operator=="add":
        print "Your answer is", a + b
    if operator=="subtract":
        print "Your answer is", a - b    
    repeat=raw_input("Do you want to perform another calculation(yes or no)? ")
    if repeat == 'no':
        break

当True永远继续循环时，它可以被关键字break打断（它从最近的循环中打断（for或While））。

当处理用户的输入以确定条件时，最好检查用户的输入是以"y"（是）开头还是以"n"（否）开头，因为用户可能会输入y而不是"是"，他可能会混淆大写，这里有一个代码可以实现这一点：

while True:
    a,b=input("Enter two numbers (sperated by a comma): ")
    operator=raw_input("Do you want to add, subtract, multiply, or divide? ")
    if operator=="divide":
        print "Your answer is", a / b
    if operator=="multiply":
        print "Your answer is", a * b
    if operator=="add":
        print "Your answer is", a + b
    if operator=="subtract":
        print "Your answer is", a - b    
    repeat=raw_input("Do you want to perform another calculation(yes or no)? ")
    if repeat.lower.startswith('n'):
        break 

"repeat"是一个字符串，它有一个名为"lower"的方法（类似于函数），该方法返回字符串的小写表示形式，然后您可以使用另一个称为startswith的方法来检查该小写表示形式（也是字符串）是否以字母"n"开头。

试试这个：

while True:    
    a,b=input("Enter two numbers (sperated by a comma): ")
    operator=raw_input("Do you want to add, subtract, multiply, or divide? ")
    if operator=="divide":
        print "Your answer is", a / b
    if operator=="multiply":
        print "Your answer is", a * b
    if operator=="add":
        print "Your answer is", a + b
    if operator=="subtract":
        print "Your answer is", a - b    
    repeat=raw_input("Do you want to perform another calculation(yes or no)? ")
    if repeat == "no":
        break

试试这个
您可以使用while True:，在for循环中编写的代码
将无限执行，
要停止执行，您可以使用Ctrl+C
while True:
    a,b=input("Enter two numbers (sperated by a comma): ")
    operator=raw_input("Do you want to add, subtract, multiply, or divide? ")
    if operator=="divide":
        print "Your answer is", a / b
    if operator=="multiply":
        print "Your answer is", a * b
    if operator=="add":
        print "Your answer is", a + b
    if operator=="subtract":
        print "Your answer is", a - b    
    repeat=raw_input("Do you want to perform another calculation(yes or no)? ")
    if repeat == "no":
        break