python - 如何让用户指定一个数字而不会向我抛出错误？

Question

我创建了一个素数生成器，并希望用户指定生成的素数的数量。我想知道如何将“1000”更改为 raw_input，而程序不会像它一直在做的那样向我抛出错误。另外，如何将生成的此列表保存到 .txt 文件中？提前致谢

代码：

no_of_primes = 1
candidate = 2
start = 2
list_of_primes = []

while no_of_primes <= 5000:
    result = candidate % start

    if result > 0:
        start +=1

    elif result == 0:
        if start == candidate:
            list_of_primes.append(candidate)
            candidate +=1
            no_of_primes +=1
            start =2
        else:
            candidate +=1
            start = 2

print list_of_primes

Answer 1

首先，将 替换5000为变量（例如，primes_to_generate）。然后在循环之前，while通过调用int. 会将其从字符串转换为数字，从而修复您的错误raw_input：int

primes_to_generate = int(raw_input("How many to generate? "))

try如果有人输入“90”而不是“90”，您还可以使用块来捕获错误：

try:
    primes_to_generate = int(raw_input("How many to generate? "))
except ValueError:
    print "Whoa! That's not a number I know!"
    # You'd probably then want to let the user retry
    # by enclosing this whole thing in a loop or something.