Python储蓄计算器报错：TypeError: can only concatenate str (not "int") to str

问题描述 #

开发简易储蓄计算器时添加用户输入功能后触发错误：TypeError: can only concatenate str (not "int") to str，实现代码如下：

def save():
    # Set the target savings amount and the number of months
    target_savings = input("Please input your savings goal.")
    print("")
    months = input("Please input how many months you want to take to reach this goal.")
    print("")

    # Initialize the current savings amount
    current_savings = 0

    # Set monthly income
    monthly_income = input("Please input your monthly income")
    print("")

    # Loop through each month
    for month in range(1, months + 1):
        # Get the monthly expenses
        expenses = float(input("Enter expenses for month {month}: $"))
        # Calculate the monthly savings
        monthly_savings = monthly_income - expenses
        # Add the monthly savings to the current savings
        current_savings += monthly_savings
        # Check if the current savings is enough to reach the target savings
        if current_savings >= target_savings:
            print(f"Congratulations! You reached your savings goal of ${target_savings} in month {month}.")
            break
        else:
            print(f"Month {month}: Savings = ${current_savings}, Goal = ${target_savings}")

# Call the function to start the savings tracker
save()

报错信息：

for month in range(1, months + 1):
TypeError: can only concatenate str (not "int") to str

错误原因 #

• input()函数返回的是字符串类型，而range()的参数需要整数。代码中months是用户输入的字符串，执行months + 1时会尝试把字符串和整数拼接，触发类型错误。
• 除此之外，target_savings和monthly_income也是字符串类型，后续执行monthly_income - expenses、current_savings >= target_savings时也会触发类型错误，只是当前报错先出现在循环部分。

修复方案 #

将用户输入的数值类变量转换为对应的数据类型：

• months转换为整数int()
• target_savings和monthly_income转换为浮点数float()（支持小数金额）

修复后的完整代码：

def save():
    # Set the target savings amount and the number of months
    target_savings = float(input("Please input your savings goal."))
    print("")
    months = int(input("Please input how many months you want to take to reach this goal."))
    print("")

    # Initialize the current savings amount
    current_savings = 0.0

    # Set monthly income
    monthly_income = float(input("Please input your monthly income"))
    print("")

    # Loop through each month
    for month in range(1, months + 1):
        # Get the monthly expenses
        expenses = float(input(f"Enter expenses for month {month}: $"))
        # Calculate the monthly savings
        monthly_savings = monthly_income - expenses
        # Add the monthly savings to the current savings
        current_savings += monthly_savings
        # Check if the current savings is enough to reach the target savings
        if current_savings >= target_savings:
            print(f"Congratulations! You reached your savings goal of ${target_savings:.2f} in month {month}.")
            break
        else:
            print(f"Month {month}: Savings = ${current_savings:.2f}, Goal = ${target_savings:.2f}")

# Call the function to start the savings tracker
save()

额外优化：添加:.2f格式化输出金额，保留两位小数，更符合金额显示习惯。

内容的提问来源于stack exchange，提问作者Kaleb Elley