不知道为什么我得到“TypeError：只能将str（而不是“int”）连接到str”

Question

我有工作代码，但它每年都给我相同的Invest_amount（没有添加上一年的兴趣），所以我创建了一个Starting_balance 来尝试解决这个问题。

但是，现在它给了我这个错误信息：

TypeError: can only concatenate str (not "int") to str. But I put str in front of the value?

我的代码：

InvestAmount = int(input("Enter the intial investment amount: "))
Years = int(input("Enter the number of years to invest: "))
Rate = float(input("Enter the intrest rate (as %): "))
TotalInterestEarned = 0
for i in range(Years):
     InterestEarned = round(InvestAmount*(Rate/100),2)
     EndingBal = round(InvestAmount+InterestEarned , 2)
     Starting_balance = (InvestAmount + InterestEarned)
     print("Starting Balance: for year " + (i+1)+"$"+str(Starting_balance))    
     print("Ending balance: for year" +(i+1)+"$"+str(EndingBal))
     print("Total interest earned: for year" +(i+1)+"$"+str(InterestEarned))

Answer 1

"abc" + (i+1) 正在向字符串添加一个整数。考虑使用这样的 f 字符串：

print(f"Starting Balance: for year {i+1} ${Starting_balance}")

它更具可读性并为您执行所需的转换。

Answer 2

你只能连接两个字符串，你试图连接 int 和 str

InvestAmount = int(input("Enter the intial investment amount: "))
Years = int(input("Enter the number of years to invest: "))
Rate = float(input("Enter the intrest rate (as %): "))



TotalInterestEarned = 0
for i in range(Years):
      InterestEarned = round(InvestAmount*(Rate/100),2)
      EndingBal = round(InvestAmount+InterestEarned , 2)
      Starting_balance = (InvestAmount + InterestEarned)
      
      print("Starting Balance: for year " + str((i+1))+"$"+str(Starting_balance))  # change int to str as well str(i+1)  
      print("Ending balance: for year" +str((i+1))+"$"+str(EndingBal)) # same here 
      print("Total Interest Earned: for year" +str((i+1))+"$"+str(InterestEarned)) # same here

Answer 3

每个人都已经大致了解了解决方案，但我希望可以为那些不熟悉类型的人添加更多上下文。所以当你定义 i 时，它是一个 int。另一方面，您尝试放入的字符串是“Starting Balance:...”，这意味着它是一个字符串。使用整数5 + 5 = 10。添加整数是标准的。同样，python 足够聪明，可以理解"con" + "cat" = "concat"，因为本质上你是在字符串的末尾。

现在，当您执行 "con" + 5 = ERROR 时会发生什么，因为 python 不理解将整数添加到字符串意味着什么。这是否意味着您应该将 "con" 转换为整数表示并以这种方式添加 5，或者是否意味着将数字 5 添加到 "con5"？ （请注意，某些语言允许这种添加，但有时会变得很奇怪。Python 是强类型的，因此我们不必考虑这种可能性。）

换句话说，我们必须做出区分，否则我们的类型不匹配。在所有的解决方案中，我们正在将i+1 转换为某个字符串，通过制定str() 或f-strings。

希望这可以澄清！

Answer 4

你可以这样做：

print(f"Starting Balance: for year {i+1} $ {Starting_balance}") 
# and other code... 

Answer 5

您只需要像这样将str 添加到 (i+1) 之前：

print("Starting Balance: for year " + str((i + 1)) + " $" + str(Starting_balance))
print("Ending balance: for year " + str((i + 1)) + " $" + str(EndingBal))
print("Total Interest Earned: for year " + str((i + 1)) + " $" + str(InterestEarned))

Answer 6

为了完整起见，另一种方法是使用 , 并让 print 函数完成它的工作。

打印函数接受单个对象或多个对象，以,分隔，并将转换为字符串并打印在屏幕上。

InvestAmount = int(input("Enter the intial investment amount: "))
Years = int(input("Enter the number of years to invest: "))
Rate = float(input("Enter the intrest rate (as %): "))


TotalInterestEarned = 0
for i in range(Years):
    InterestEarned = round(InvestAmount * ( Rate / 100),2)
    EndingBal = round(InvestAmount + InterestEarned , 2)
    Starting_balance = (InvestAmount + InterestEarned)
      
    print("Starting Balance: for year ", (i + 1), "$", Starting_balance)    
    print("Ending balance: for year", (i + 1), "$", EndingBal)
    print("Total Interest Earned: for year", (i + 1), "$", InterestEarned)

这不是最好的方法，其他答案要好得多。