In python, what is the fastest way to determine if a string is an email or an integer?

Question

I'd like to be able to pull users from a database using either a supplied e-mail address or the user id (an integer). To do this, I have to detect if the supplied string is an integer, or an e-mail. Looking for the fastest way to do this. Thanks.

def __init__(self, data):
    #populate class data
    self._fetchInfo(data)


def _fetchInfo(self, data):
    #If an email
        #SELECT ... WHERE email = 'data'
    #or if a user_id
        #SELECT ... WHERE id = 'data'

    #Fill class attributes 
    self._id = row['id']
    self._email = row['id']
    ...

Answer 1

The canonical way to handle this in Python is to try first, ask forgiveness later:

def _fetchInfo(self, data):
    try:
        data=int(data)
        sql='SELECT ... WHERE id = %s'
        args=[data]
    except ValueError:
        sql='SELECT ... WHERE email = %s'
        args=[data]
        # This might fail, in which case, data was neither a valid integer or email address

This strategy also goes by the moniker "It is Easier to Ask for Forgiveness than Permission".

Answer 2

You can use the isinstance function:

if isinstance(data, int):
   # it's an id
else:
   # it's a string

Though personally, I'd just have two methods, fetchById and fetchByEmail to make it clear that's how it works.

Answer 3

You said both were strings, right? This would work, too.

if data.isdigit():
    # it's an id
else:
    # it's not

Answer 4

if '@' in data:
    # email
else:
    # id