Question

我正在编写一个简单的代码来计算应付的更改量，并使用print语句来检查我的值。

cost = float(raw_input('How much did your meal cost? > '))
payment = float(raw_input('How much did you pay? > '))

change = (payment - cost)

print change

if change < 0:
    print 'You need to pay $%.2f more!' %  (-change)

dollars, q, d, n, p = 0, 0, 0, 0, 0

change = float(change*100)

print change

if change> 100:
    dollars = int(change/100)
    change = change % 100
    print change

if change >= 25:
    q = int(change/25)
    change = change % 25
    print change

if change >= 10:
    d = int(change/10)
    change = change % 10
    print change

if change >= 5:
    n = int(change/5)
    change = change % 5
    print change    

if change >= 1:
    p = int(change/1)
else:
    print "why doesn't this work?"
    print p
    print change

print 'you get %d dollars, %d quarters, %d dimes, %d nickels, and %d pennies!' % (dollars, q, d, n, p)

返回：

您的餐费是多少？＆GT; 34.34

你付多少钱？＆GT; 40

5.66

566.0

66.0

16.0

6.0

1.0

为什么这不起作用？

0

1.0

我可以在便士计算之前和之后看到变化= 1.0，但是

if change >= 1

仍然显示为false，并转到else语句。这里发生了什么，我该如何解决？

Answer 1

欢迎使用IEEE 754浮点数。享受inaccuracies。如果要避免它们，请使用定点或整数机制。

Answer 2

请阅读：浮点运算：问题与限制

http://docs.python.org/2/tutorial/floatingpoint.html

您可能对Decimal模块

感兴趣

Answer 3

浮子（40）-float（34.34）= 5.659999999999997

我猜你说“change = 1.0”不是1.0，而是0.99999999999

尝试：round(40-34.34, 2)

Answer 4

正如伊格西奥所说的那样。简单的解决方法就是抛出一条线来改变第二个小数位。使用函数简化一些事情，您的代码变为：

def get_change_and_coin(coin_amount, change):
    change = round(change, 2)
    return (change % coin_amount, int(change / coin_amount))


cost = float(raw_input('How much did your meal cost? > '))
payment = float(raw_input('How much did you pay? > '))

change = (payment - cost)

print change

if change < 0:
    print 'You need to pay $%.2f more!' %  (-change)

dollars, q, d, n, p = 0, 0, 0, 0, 0

dollars = int(change)
change = float(change*100)

(change, q) = get_change_and_coin(25, change)
(change, d) = get_change_and_coin(10, change)
(change, n) = get_change_and_coin(5, change)
(change, p) = get_change_and_coin(1, change)

print 'you get %d dollars, %d quarters, %d dimes, %d nickels, and %d pennies!' % (dollars, q, d, n, p)

希望这有帮助！

Python代码不起作用 - 关于if语句的混淆

4 个答案: