Python输入验证-接受正浮点或整数 [英] Python Input validation - positive float or int accepted

问题描述

似乎我们提出了很多要求，但是我们正在寻求对输入的正整数或浮点数进行简短验证.下面的代码拒绝否定，文本和空条目-是的！它接受int为有效，但是为什么不通过1.1这样的输入呢? (看似正数输入)我们希望正1和1.1的输入通过.没有两个单独的块(包括try/catch)，有没有简单的方法?

seems we are asking a lot, but we are seeking a short validation for positive int or float being entered as input. The code below rejects negative, text and null entries - yay! It accepts int as valid, but why doesn't entry like 1.1 pass? (seemingly a positive numeric entry) We want entry of positive 1 and 1.1 to pass. is there an easy way without two separate blocks, including try/catch?

bookPrice = input("What is the cost of your book? >> ")
while bookPrice.isnumeric() is False or float(bookPrice) < 0:
    bookPrice = input("Use whole # or decimal, no spaces: >> ")
bookPrice = float(bookPrice)
print("Your book price is ${0:<.2f}.".format(bookPrice))

推荐答案

isnumeric()正在检查所有字符是否都是数字(例如1、2、100 ...).

isnumeric() is checking if all the characters are numeric (eg 1, 2, 100...).

如果您输入."在输入中，它既不算作数字字符，也不算作'-'，因此它返回False.

If you put a '.' in the input, it doesn't count as a numeric character, nor does '-', so it returns False.

我要做的是尝试将输入转换为 float ，并解决输入错误的问题. 您本可以使用 isinstance() ，但是为此您会需要将输入内容转换为 string 以外的其他内容.

What I would do is try to convert the input to float, and work around bad inputs. You could've used isinstance(), but for that you would need to convert the input to something else than string.

我想到了这个

message = "What is the cost of your book? >>"
while True:
    bookPrice = input(message)
    try:
        bookPrice = float(bookPrice)

        if bookPrice  <= 0:
            message = "Use whole # or decimal, no spaces: >> "
            continue
        currect_user_input = True

    except ValueError:
        currect_user_input = False
        message = "Use whole # or decimal, no spaces: >> "

    if currect_user_input:
        print("Your book price is ${0:<.2f}.".format(bookPrice))
        break

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