from operator import itemgetter

l =[{'value': 'apple', 'blah': 2}, 
 {'value': 'banana', 'blah': 3} , 
 {'value': 'cars', 'blah': 4}]

#option 1
new_list_1 = list(map(itemgetter("value")))


#option 2
def get_value(i):
    return i["value"]
new_list_2 = list(map(get_value, l))