是用字母还是字母来限制输入？（Python）

Question

初级python用户！我正在写一个小费计算器，它会给你的饭量增加小费，但我遇到了一个问题。这是我需要帮助的代码。在

bill_amt = True
while bill_amt:
    bill_amt = float(input('First, what was the price of your meal?(Please do not use signs such as "$"):'))
    if bill_amt <= 0: #or if bill_amt has letters or symbols
        print('Your meal wasn\'t $',bill_amt, '! Please try again.')
        bill_amt = True
    else:
        x = float(bill_amt)
        bill_amt = False

我希望能够添加到if bill_amt <= 0:命令，该命令还将捕获符号（不包括句点）和字母，这样如果您输入的价格是54.65美元或56.ad，那么您必须输入正确的输入。谢谢，如果这是复制品，对不起！-便盆

Answer 1

像这样的东西会有用的。在

bill_amt = True
while bill_amt:
    try:
        bill_amt = float(input('First, what was the price of your meal?(Please do not use signs such as "$"):'))
    except ValueError:
        print('Please enter just a number')
        continue
    if bill_amt <= 0: #or if bill_amt has letters or symbols
        print('Your meal wasn\'t $',bill_amt, '! Please try again.')
        bill_amt = True
    else:
        x = float(bill_amt)
        bill_amt = False