def isPhoneNumber(text):

if len(text) != 12:

return False # not phone number-sized

for i in range(0, 3):

if not text[i].isdecimal():

return False # not an area code

if text[3] != '-':

return False # does not have first hyphen

for i in range(4, 7):

if not text[i].isdecimal():

return False # does not have first 3 digits

if text[7] != '-':

return False # does not have second hyphen

for i in range(8, 12):

if not text[i].isdecimal():

return False # does not have last 4 digits

return True # "text" is a phone number!

print('415-555-4242 is a phone number:')

print(isPhoneNumber('415-555-4242'))

print('Moshi moshi is a phone number:')

print(isPhoneNumber('Moshi moshi'))