Python Add Comma Into Number String

Question

Using Python v2, I have a value running through my program that puts out a number rounded to 2 decimal places at the end:

like this:

print (\"Total          


        

Answer 1

A function that works in python2.7+ or python3.1+

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()!")

Answer 2

Started learning Python about 5 hours ago, but I think I came up with something for integers (sorry, couldn't figure out floats). I'm in high school, so big chance the code could be way more efficient; I just made something from scratch that made sense to me. If anyone has any ideas on how to improve with ample explanation of how it works, let me know!

# 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

Answer 3

You could use locale.currency if TotalAmount represents money. It works on Python <2.7 too:

>>> locale.setlocale(locale.LC_ALL, '')
'en_US.utf8'
>>> locale.currency(123456.789, symbol=False, grouping=True)
'123,456.79'

Note: it doesn't work with the C locale so you should set some other locale before calling it.

Answer 4

if you are using Python 3 or above, here is an easier way to insert a comma:

First way

value = -12345672
print (format (value, ',d'))

or another way

value = -12345672
print ('{:,}'.format(value)) 

Answer 5

The above answers are so much nicer than the code I was using in my (not-homework) project:

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

Answer 6

I feel comfortable using like this in python:

input_value=float(input())
print("{:,}".format(input_value))