我一直在寻找答案,只发现了我的问题。 我通过这个过程来评论代码,说明哪些有效,哪些无效 我为每一行得到了什么错误。提前谢谢。
#
# list_of_numbers is a list with numbers
# like '3.543345354'
#
# I want to change to a number with two places
#
#
# for each item in the list
for idx, value in enumerate(list_of_numbers):
# make sure it is not none
if value != None:
#
# convert to a float - this works
temp_val = float(value)
# test and print the format - yep this works
print("%.2f" % temp_val)
# store in a new variable - works
formatted_number = "%.2f" % temp_val
# check - yep looks good so far. the line blow will print 3.54 etc
print formatted_number
#
# now try to store it back
#
# the below two lines when I try both give me the
# unsupported operand type(s) for +: 'float' and 'str'error
list_of_numbers[idx] = formatted_number
list_of_numbers[idx] = '%s' % formatted_number
#
# the line below give me the error
# float argument required, not str
list_of_numbers[idx] = '%f' % formatted_number
#
# so from the above error formatted_number is a string.
# so why cant I set the variable with the string
#
# the ONLY thing that works is the lone below but I
# dont want an integer
#
list_of_numbers[idx] = int(float(value ))
答案 0 :(得分:7)
您需要round
功能:
n2 = round(n, 2)
另外,要预先警告:花车是不精确的,当你转到两个地方,然后打印它们,它们可能看起来像它们有更多。您需要在格式字符串中使用%.2f
来显示两个位置。如果你需要绝对的精确度(比如金钱),Decimal
对你来说可能更好。