Converting Float to Dollars and Cents

Building on @JustinBarber's example and noting @eric.frederich's comment, if you want to format negative values like -$1,000.00 rather than $-1,000.00 and don't want to use locale:

def as_currency(amount):
    if amount >= 0:
        return '${:,.2f}'.format(amount)
    else:
        return '-${:,.2f}'.format(-amount)

Personally, I like this much better (which, granted, is just a different way of writing the currently selected "best answer"):

money = float(1234.5)
print('$' + format(money, ',.2f'))

Or, if you REALLY don't like "adding" multiple strings to combine them, you could do this instead:

money = float(1234.5)
print('${0}'.format(format(money, ',.2f')))

I just think both of these styles are a bit easier to read. :-)

(of course, you can still incorporate an If-Else to handle negative values as Eric suggests too)

In python 3, you can use:

import locale
locale.setlocale( locale.LC_ALL, 'English_United States.1252' )
locale.currency( 1234.50, grouping = True )

Output

'$1,234.50'

In Python 3.x and 2.7, you can simply do this:

>>> '${:,.2f}'.format(1234.5)
'$1,234.50'

The :, adds a comma as a thousands separator, and the .2f limits the string to two decimal places (or adds enough zeroes to get to 2 decimal places, as the case may be) at the end.