For the following nested list, Lst, I need to keep the first inner list, square the second, and cube the last one.
Lst = [[1,2,3],[2,3,4],[3,4,5]]
My current code is squaring all the nested list in the Lst.
list(map(lambda lst: list(map(lambda x: x**2, lst)), Lst))
How can I fix this? I just started learning Python.
Since you're not doing the same operation on each nested list, you shouldn't use map() for the top-level list. Just make a list of results of different mappings for each.
[Lst[0], list(map(lambda x: x**2, lst[1])), list(map(lambda x: x**3, lst[2]))]
However, there's an obvious pattern to this, so you can generalize it using enumerate() and a list comprehension:
[list(map(lambda x: x**i, sublist)) for i, sublist in enumerate(Lst, 1)]
[list(map(lambda x: x**i, l)) for i,l in enumerate(Lst, 1)]
[[1, 2, 3], [4, 9, 16], [27, 64, 125]]
Your processing obviously needs to take into account where in the list you are. Forcing this into a one-liner makes it more dense than it really needs to be, but see if you can follow along with pencil and paper.
[[x if i == 0 else x**2 if i == 1 else x**3 for x in Lst[i]] for i in range(3)]
Demo: https://ideone.com/o8y0ta
... Or, as cleverly suggested in Barmar's answer,
[[x**i for x in Lst[i]] for i in range(3)]
Try indexing the outer list and then call the map function on each index
def square(number) :
return number ** 2
def cube(number) :
return number ** 3
lst = [[1,2,3],[2,3,4],[3,4,5]]
lst[0] = lst[0]
lst[1] = list(map(square, lst[1]))
lst[2] = list(map(cube, lst[2]))
print(lst)
