从美分到美元的数字格式

Posted 2023-04-14

【中文标题】从美分到美元的数字格式

【英文标题】：Number formatting from cents to dollars

【发布时间】：2013-03-14 04:26:40

【问题描述】：

我正在尝试使用 Python 2.7 的字符串格式以美元输出十个苹果的成本，其中单价以美分提供。

我希望total_apple_cost 的值为"10.00"，但它是"1.001.001.001.001.001.001.001.001.001.00"。

我已经对其他变量进行了测试，以表明它们都按预期出现：

# define apple cost in cents
apple_cost_in_cents = 100
# define format string
cents_to_dollars_format_string = ':,.2f'
# convert 100 to 1.00
apple_cost_in_dollars = cents_to_dollars_format_string.format(apple_cost_in_cents / 100.)
# assign value of 'apple_cost_in_dollars' to 'apple_cost'
apple_cost = apple_cost_in_dollars
# calculate the total apple cost
total_apple_cost = 10 * apple_cost

# print out the total cost
print 'total apple cost: ' + str(total_apple_cost) + '\n'

#testing
print 'cost in cents: ' + str(apple_cost_in_cents) + '\n'
print 'cost in dollars: ' + str(apple_cost_in_dollars) + '\n'
print 'apple cost: ' + str(apple_cost) + '\n' 

解决方案：

感谢您在下面给出的答案都表明变量“apple_cost_in_dollars”是一个字符串。

我的解决方案是将其设为浮点数并保持其余代码几乎相同：

apple_cost_in_cents = 100
cents_to_dollars_format_string = ':,.2f'
apple_cost_in_dollars = float(cents_to_dollars_format_string.format(apple_cost_in_cents / 100.))
apple_cost = apple_cost_in_dollars
total_apple_cost = 10 * apple_cost

print 'cost in cents: ' + str(apple_cost_in_cents) + '\n'

print 'cost in dollars: $'':,.2f'.format(apple_cost_in_dollars) + '\n'

print 'apple cost: $'':,.2f'.format(apple_cost) + '\n'

print 'total apple cost: $'':,.2f'.format(total_apple_cost) + '\n'

【参考方案1】：

这是因为apple_cost_in_dollars是一个字符串，见下文

In [9]: cost = '1'

In [10]: cost * 10
Out[10]: '1111111111'

In [11]: cost = int('1')

In [12]: cost * 10
Out[12]: 10

【参考方案2】：

apple_cost 是一个字符串，您将其乘以 10（它只是将字符串重复 10 次）。在将其格式化为字符串之前先转换为美元。

>>> apple_cost_in_cents = 100
>>> cents_to_dollars_format_string = ':,.2f'
>>> total_apple_cost_in_dollars_as_string = cents_to_dollars_format_string.format(10*apple_cost_in_cents/100.0)
>>> total_apple_cost_in_dollars_as_string
'10.00'

如果您想进一步格式化货币，可以查看locale 模块，特别是locale.currency 函数。

【参考方案3】：

>>> import locale
>>> apple_cost_in_cents = 100
>>> locale.setlocale(locale.LC_ALL, '')
'en_US.UTF-8'
>>> locale.currency(apple_cost_in_cents * 10 / 100)
'$10.00'

【参考方案4】：

它被格式化为字符串（文本）。所以如果你写 10 * string_variable，它只是重复那个字符串 10 次。最简单的方法是更改​​这一行：

total_apple_cost = 10 * apple_cost

到：

total_apple_cost = cents_to_dollars_format_string.format(10 * apple_cost_in_cents/100)