age = 99
print ("i'm " + str(age) +" years old")
print ("i'm {0} years old".format(age)) # string literals
print('there are {0} days in {1}, {2}, {3}, {4}, {5}, {6} and {7}'.format(31, "Jan", "Mar", "May", "Jul", "Aug", "Oct", "Dec"))
print('Jan: {1}, Feb: {2}, Mar: {1}, Apr: {3}'.format(31,28,30))