sort tuple by first element python

a = [(5,8), (3,4), (9,7)]

#sort by first element in tuple
result = sorted(a, key=lambda tup: tup[0])

#OR to do inplace sort:

a.sorted(key = lambda tup: tup[0])

# output
[(3, 4), (5, 8), (9, 7)]

# lists_of_tuples = [('item', 'price'), ('item', 'price'), ('item', 'price')]
def sort_prices(list_of_tuples): #sort the list b*y the price of each tuple
    list_of_tuples.sort(key=lambda x: x[1], reverse=True) #earse the "reverse" part to sort in small to big.
    return list_of_tuples, print(list_of_tuples)