字符串上的 .removeprefix() 方法什么都不做

Question

输入输入后，比如 50.00 美元，我收到一条错误消息 ValueError: could not convert string to float: '.00'。我在第 10 行已经有了 dollars.removeprefix("$")，.removeprefix() 方法什么都不做。我究竟做错了什么？完整代码如下：

def main():
    dollars = dollars_to_float(input("How much was the meal? "))
    percent = percent_to_float(input("What percentage would you like to tip? "))
    percent = percent / 100
    tip = dollars * percent
    print(f"Leave ${tip:.2f}")


def dollars_to_float(dollars):
    dollars.removeprefix("$")
    return float(dollars)


def percent_to_float(percent):
    percent.removesuffix("%")
    return float(percent)


main()

Answer 1

您没有将结果重新分配给变量。

def main():
    dollars = dollars_to_float(input("How much was the meal? "))
    percent = percent_to_float(input("What percentage would you like to tip? "))
    percent = percent / 100
    tip = dollars * percent
    print(f"Leave ${tip:.2f}")


def dollars_to_float(dollars):
    dollars = dollars.removeprefix("$")
    return float(dollars)


def percent_to_float(percent):
    percent = percent.removesuffix("%")
    return float(percent)

您真的应该改进您的代码以执行更多的输入验证。如果我这样做，您的脚本会怎样？

>>> How much was the meal? 
>>> 50$

一个让它更健壮的简单想法：

import re

def dollars_to_float(dollars):
    # Extract numbers, ignore all else
    dollars = re.sub(r"[^1-9\.]", "", dollars)
    return float(dollars)

字符串上的 .removeprefix() 方法什么都不做

.removeprefix() method on a string does nothing

python