如何在将Python2中生成的文件传输到Python3时修复代码

如何修复代码：

Subtotal = input("What is your Subtotal? ")
input_tax = input('What is the Tax? Please enter as a decimal ')
input_tip  = input('What is the Tip? Please enter as a decimal ')
Tax = float(input_tax) * float(Subtotal)
Tip = float(input_tip) * float(Subtotal)
Total = float(Tip) + float(Tax) + float(Subtotal)
print ("Your Total is $") + str(Total)

Traceback (most recent call last):
  File "C:\Python27\Tip_and_Tax_Calculator.py", line 7, in <module>
    print ("Your Total is $") + str(Total)
TypeError: unsupported operand type(s) for +: 'NoneType' and 'str'`

当错误消息为：

Subtotal = input("What is your Subtotal? ")
input_tax = input('What is the Tax? Please enter as a decimal ')
input_tip  = input('What is the Tip? Please enter as a decimal ')
Tax = float(input_tax) * float(Subtotal)
Tip = float(input_tip) * float(Subtotal)
Total = float(Tip) + float(Tax) + float(Subtotal)
print ("Your Total is $") + str(Total)

Traceback (most recent call last):
  File "C:\Python27\Tip_and_Tax_Calculator.py", line 7, in <module>
    print ("Your Total is $") + str(Total)
TypeError: unsupported operand type(s) for +: 'NoneType' and 'str'`

回溯（最近一次呼叫最后一次）：
文件“C:\Python27\Tip\u and\u Tax\u Calculator.py”，第7行，在
打印（“您的总数为$”）+str（总数）
TypeError:不支持+：“NoneType”和“str”的操作数类型`

只需将

str（总计）

移到括号内即可。在Python中，3是一个函数。因此，现在Python正在尝试将

print

（始终为

None

）的返回值添加到

str（Total）

（这是一个字符串）

Subtotal = input("What is your Subtotal? ")
input_tax = input('What is the Tax? Please enter as a decimal ')
input_tip  = input('What is the Tip? Please enter as a decimal ')
Tax = float(input_tax) * float(Subtotal)
Tip = float(input_tip) * float(Subtotal)
Total = float(Tip) + float(Tax) + float(Subtotal)
print ("Your Total is $") + str(Total)

Traceback (most recent call last):
  File "C:\Python27\Tip_and_Tax_Calculator.py", line 7, in <module>
    print ("Your Total is $") + str(Total)
TypeError: unsupported operand type(s) for +: 'NoneType' and 'str'`

因此，将最后一行更改为：

Subtotal = input("What is your Subtotal? ")
input_tax = input('What is the Tax? Please enter as a decimal ')
input_tip  = input('What is the Tip? Please enter as a decimal ')
Tax = float(input_tax) * float(Subtotal)
Tip = float(input_tip) * float(Subtotal)
Total = float(Tip) + float(Tax) + float(Subtotal)
print ("Your Total is $") + str(Total)

Traceback (most recent call last):
  File "C:\Python27\Tip_and_Tax_Calculator.py", line 7, in <module>
    print ("Your Total is $") + str(Total)
TypeError: unsupported operand type(s) for +: 'NoneType' and 'str'`

print（“您的总数为$”+str（总数））

---

此外，在Python 3中，您可以使用更优雅的方式格式化字符串：

Subtotal = input("What is your Subtotal? ")
input_tax = input('What is the Tax? Please enter as a decimal ')
input_tip  = input('What is the Tip? Please enter as a decimal ')
Tax = float(input_tax) * float(Subtotal)
Tip = float(input_tip) * float(Subtotal)
Total = float(Tip) + float(Tax) + float(Subtotal)
print ("Your Total is $") + str(Total)

Traceback (most recent call last):
  File "C:\Python27\Tip_and_Tax_Calculator.py", line 7, in <module>
    print ("Your Total is $") + str(Total)
TypeError: unsupported operand type(s) for +: 'NoneType' and 'str'`

• 对于Python>=3.0：字符串方法：

  Subtotal = input("What is your Subtotal? ")
  input_tax = input('What is the Tax? Please enter as a decimal ')
  input_tip  = input('What is the Tip? Please enter as a decimal ')
  Tax = float(input_tax) * float(Subtotal)
  Tip = float(input_tip) * float(Subtotal)
  Total = float(Tip) + float(Tax) + float(Subtotal)
  print ("Your Total is $") + str(Total)
  

  Traceback (most recent call last):
    File "C:\Python27\Tip_and_Tax_Calculator.py", line 7, in <module>
      print ("Your Total is $") + str(Total)
  TypeError: unsupported operand type(s) for +: 'NoneType' and 'str'`
  

• 对于Python>=3.6:：

  Subtotal = input("What is your Subtotal? ")
  input_tax = input('What is the Tax? Please enter as a decimal ')
  input_tip  = input('What is the Tip? Please enter as a decimal ')
  Tax = float(input_tax) * float(Subtotal)
  Tip = float(input_tip) * float(Subtotal)
  Total = float(Tip) + float(Tax) + float(Subtotal)
  print ("Your Total is $") + str(Total)
  

  Traceback (most recent call last):
    File "C:\Python27\Tip_and_Tax_Calculator.py", line 7, in <module>
      print ("Your Total is $") + str(Total)
  TypeError: unsupported operand type(s) for +: 'NoneType' and 'str'`
  

---

print（“您的总数是$”+str（Total））

。这是因为在Python 3中

print

返回

None

。您可以使用Python>=3.6执行

print（您的总数是${Total}'）