使用 Python v2，我的程序中运行着一个值 最后给出一个四舍五入到小数点后两位的数字：
像这样：
print ("Total cost is: ${:0.2f}".format(TotalAmount))
有没有办法在小数点左边每 3 位插入一个逗号值？
即：10000.00 变为 10,000.00 或 1000000.00 变为 1,000,000.00
感谢您的帮助。
【问题讨论】：
在 Python 2.7 和 3.x 中，您可以使用格式语法:,
>>> total_amount = 10000
>>> print("{:,}".format(total_amount))
10,000
>>> print("Total cost is: ${:,.2f}".format(total_amount))
Total cost is: $10,000.00
这在PEP 378 -- Format Specifier for Thousands Separator 中有记录，在Official Docs "Using the comma as a thousands separator" 中有一个示例
【讨论】：
如果您使用的是 Python 3 或更高版本，以下是插入逗号的更简单方法：
value = -12345672
print (format (value, ',d'))
value = -12345672
print ('{:,}'.format(value))
【讨论】：
format(value, ",f")
如果TotalAmount 代表金钱，您可以使用locale.currency。它也适用于 Python
>>> locale.setlocale(locale.LC_ALL, '')
'en_US.utf8'
>>> locale.currency(123456.789, symbol=False, grouping=True)
'123,456.79'
注意：它不适用于 C 语言环境，因此您应该在调用它之前设置一些其他语言环境。
【讨论】：
'{:20,.2f}'.format(TotalAmount)
【讨论】：
这不是特别优雅，但也应该可以：
a = "1000000.00"
e = list(a.split(".")[0])
for i in range(len(e))[::-3][1:]:
e.insert(i+1,",")
result = "".join(e)+"."+a.split(".")[1]
【讨论】：
一个在python2.7+或python3.1+中工作的函数
def comma(num):
'''Add comma to every 3rd digit. Takes int or float and
returns string.'''
if type(num) == int:
return '{:,}'.format(num)
elif type(num) == float:
return '{:,.2f}'.format(num) # Rounds to 2 decimal places
else:
print("Need int or float as input to function comma()!")
【讨论】：
另一种很短的方法是
value = -122212123.12
print(f"{value:,}")
【讨论】：
上面的答案比我在我的（非家庭作业）项目中使用的代码好得多：
def commaize(number):
text = str(number)
parts = text.split(".")
ret = ""
if len(parts) > 1:
ret = "."
ret += parts[1] # Apparently commas aren't used to the right of the decimal point
# The -1 offsets to len() and 0 are because len() is 1 based but text[] is 0 based
for i in range(len(parts[0]) - 1,-1,-1):
# We can't just check (i % 3) because we're counting from right to left
# and i is counting from left to right. We can overcome this by checking
# len() - i, although it needs to be adjusted for the off-by-one with a -1
# We also make sure we aren't at the far-right (len() - 1) so we don't end
# with a comma
if (len(parts[0]) - i - 1) % 3 == 0 and i != len(parts[0]) - 1:
ret = "," + ret
ret = parts[0][i] + ret
return ret
【讨论】：
大约 5 小时前开始学习 Python，但我想我想出了一些关于整数的东西（抱歉，无法计算浮点数）。我在高中，所以代码效率更高的可能性很大；我只是从头开始做了一些对我有意义的东西。如果有人对如何改进有任何想法并充分解释其工作原理，请告诉我！
# Inserts comma separators
def place_value(num):
perm_num = num # Stores "num" to ensure it cannot be modified
lis_num = list(str(num)) # Makes "num" into a list of single-character strings since lists are easier to manipulate
if len(str(perm_num)) > 3:
index_offset = 0 # Every time a comma is added, the numbers are all shifted over one
for index in range(len(str(perm_num))): # Converts "perm_num" to string so len() can count the length, then uses that for a range
mod_index = (index + 1) % 3 # Locates every 3 index
neg_index = -1 * (index + 1 + index_offset) # Calculates the index that the comma will be inserted at
if mod_index == 0: # If "index" is evenly divisible by 3
lis_num.insert(neg_index, ",") # Adds comma place of negative index
index_offset += 1 # Every time a comma is added, the index of all items in list are increased by 1 from the back
str_num = "".join(lis_num) # Joins list back together into string
else: # If the number is less than or equal to 3 digits long, don't separate with commas
str_num = str(num)
return str_num
【讨论】：
我觉得在 python 中这样使用很舒服：
input_value=float(input())
print("{:,}".format(input_value))
【讨论】：
最新版本的 python 使用 f-strings。所以你可以这样做：
print("Total cost: {total_amount:,}
只要 total_amount 不是字符串。否则，您需要先将其转换为数字类型，如下所示：
print("Total cost: {Decimal(total_amount):,}
【讨论】：