我刚刚开始学习 python，通过“像计算机科学家一样思考”这本书，我被一些语言语法卡住了。
def amt():
amount = input("Enter your amount: ")
amount = int(amount)
if amount >= 20:
twe = amount / 20
amount = amount - twe * 20
print("You need to pay %d twenty dollar bills" %(twe))
if amount >= 10:
ten = amount / 10
amount = amount - ten * 10
print("You need to pay %d ten dollar bills" %(ten))
if amount >= 5:
five = amount / 5
amount = amount - five * 5
print("You need to pay %d five dollar bills" %(five))
if amount >= 1:
one = amount / 1
amount = amount - one * 1
print("You need to pay %d one dollar bills" %(one))
amt()
当我使用输入 7 运行此命令时，我收到如下错误消息:
Traceback (most recent call last):
File "dollars.py", line 21, in <module>
amt()
File "dollars.py", line 7, in amt
print("You need to pay %d twenty dollar bills" %(twe))
UnboundLocalError: local variable 'twe' referenced before assignment
为什么 if 语句不能正常工作？即使输入值小于 20，它仍然进入第一个 if 语句
请您参考如下方法:
它在视觉上并不明显，但您混合了制表符和空格。看起来 print 语句在 if 中，但实际上不是。
这是您的源代码在 Stack Overflow 的文本编辑器中的样子:
