gmail_check_credentials.py

# Make sure less secure apps access is enabled on your gmail account.
# https://support.google.com/accounts/answer/6010255?hl=en

def gmail_checker(username,password):
    import imaplib
    i=imaplib.IMAP4_SSL('imap.gmail.com')
    try:
        i.login(username,password)
        if i.welcome and "OK Gimap" in i.welcome :
            return True
    except:
        return

# Use in your scripts as follows:

if ( gmail_checker('user','pass')) :
    print("Valid Credentials")
else:
    print("Invalid Credentials")