Python 不支持的操作数类型，带浮点数的逗号

我试图从用户输入中收集一个数字量，将其转换为浮点，在浮点中添加逗号，然后再次将其转换为字符串，以便使用Python打印它

这是我的密码：

usr_name = raw_input("- Please enter your name: ")
cash_amt = raw_input("- " + usr_name +", please enter the amount of money to be discounted: $")
discount_rate = raw_input("- Please enter the desired discount rate: ")
num_years = raw_input("- Please enter the number of years to discount: ")
npv = 0.0

usr_name = str(usr_name)

cash_amt = float(cash_amt)
cash_amt = round(cash_amt, 2)
cash_amt = "{:,}".format(cash_amt)

discount_rate = float(discount_rate)
num_years = float(num_years) 
npv = float(npv)

discount_rate = (1 + discount_rate)**num_years
npv = round((cash_amt/discount_rate), 2)
npv = "{:,}".format(npv)

print "\n" + usr_name + ", $" + str(cash_amt) + " dollars " + str(num_years) + " years from now 
at adiscount rate of "  + str(discount_rate) + " has a net present value of $" + str(npv)

---

当我尝试运行它时，我得到了一个与“npv=round（（现金金额/贴现率），2）”关联的“不支持的操作数类型”。我是否必须在添加逗号后将现金金额转换回浮点数？谢谢

您的代码可以缩短为以下内容：

usr_name = raw_input("- Please enter your name: ")
cash_amt = raw_input("- " + usr_name +", please enter the amount of money to be discounted: $")
discount_rate = raw_input("- Please enter the desired discount rate: ")
num_years = raw_input("- Please enter the number of years to discount: ")

 #  usr_name is  already a string
cash_amt = float(cash_amt)
cash_amt = round(cash_amt, 2)


discount_rate = float(discount_rate)
num_years = int(num_years) # we want an int to print, discount_rate  is a float so our calculations will be ok.

discount_rate = (1 + discount_rate)**num_years
npv = round((cash_amt/discount_rate), 2)


print "\n{}, ${:.2f}  dollars {} years from now at discount rate of {:.2f} has a net " \
"present value of ${}".format(usr_name,cash_amt,num_years,discount_rate,npv)

npv=float（npv）

永远不会像您当时那样实际使用

npv=round（（现金金额/贴现率），2）

而不使用您指定的第一个

npv

值

---

cash\u amt=“{}”。format（cash\u amt）

导致您的错误，因此您可以删除它并在最终打印报表中进行格式化。

回溯中的确切错误是什么？我更新了我的问题以显示确切的错误。干杯移动

cash\u amt=“{：，}”。格式化（cash\u amt）

到打印对账单之前，但实际上您应该在打印对账单中格式化它，您还将

npv

更改为浮动，而不是在重新分配到

轮（（现金金额/折扣率），2）

@philipmcquity，欢迎您。我添加了

${.2f}

，因此输出中始终有两位小数，因此

4.0

将变为

4.00

等。。