Using Python v2, I have the user entering an amount into a string as below:
RawPurchaseAmount = raw_input(\"Please enter purchase amount: \")
PurchaseAmount
Update StephenPaulger's answer is better.
Original Answer
If you don't mind regular expressions you can also replace both $ and , in one go. Something like this:
>>> import re
>>> RawPurchaseAmount
'$10,000'
>>> re.sub('[\$,]', '', RawPurchaseAmount)
'10000'
>>>
Remember to compile the regular expression if you plan to do this many times in the same program.