I have a website form that requires a US phone number input for follow up purposes, and this is very necessary in this case. I want try to eliminate users entering junk data
In Django there is a nice little contrib package called localflavor wich has a lot of country specific validation code, for example postal codes or phone numbers. You can look in the source too see how django handles these for the country you would like to use; For example: US Form validation. This can be a great recourse for information about countries you know little of as well.