Python除以0错误

Question

我目前正在使用这个Python代码:

valid_chars = "0123456789-+/* \n";
while True:
    x = "x="
    y = input(" >> ")
    x += y
    if False in [c in valid_chars for c in y]:
        print("WARNING: Invalid Equation");
        continue;
    if(y == "end"):
        break
    exec(x)
    print(x)

当用户执行类似这样的操作时崩溃:9/0.错误:

ZeroDivisionError: division by zero

有什么方法可以防止用户将某些东西除以零？

Answer 1

您可以除了ZeroDivisionError像这样

x = "1/0"
try:
    exec(x)
except ZeroDivisionError:
    print ("WARNING: Invalid Equation")

如果您使用的是Python 2.x,则输入数据将在此处进行评估

y = input(" >> ")

所以,在Python 2.x中,你应该使用

y = raw_input(" >> ")

除此之外,您可以改进这段代码

if False in [c in valid_chars for c in y]:

像这样

valid_chars = set("0123456789-+/* \n")    # We make this a set, because
if not all(c in valid_chars for c in y):  # c in valid_chars will be in O(1)

正如@gnibbler,在评论部分中建议的那样,if条件可以这样写

if any(c not in valid_chars for c in y):  # c in valid_chars will be in O(1)

另一个建议是,不需要使用半冒号来标记Python中的行尾:)