Create arrays of arrays and use dictionary-CodePudding

I have two lists:

x = ['1','5','X','9']
y = ['X','9','9P']

which I have combined like this:

z = [x,y]
print(z)

So, "z" is a list of two lists and it looks like this:

[['1', '5', 'X', '9'], ['X', '9', '9P']]

I have this dictionary:

delqType = {
    '1'  : 0,
    '2'  : 3,
    '3'  : 4,
    '4'  : 5,
    '5'  : 6,
    '7'  : 19,
    '8'  : 21,
    '8A' : 20,
    '8P' : 16,
    '9'  : 22,
    '9B' : 18,
    '9P' : 15,
    'UR' : 23,
    'X'  : -99999
    }

I want to apply the dictionary delqType to the list "z" in order to get this new list (called "t") that looks like:

[[0, 6, -99999, 22], [-99999, 22, 15]]

I have tried this code:

t = []
for i in range(len(z)):
    for j in range(len(z[i])):
        
        t.append(delqType[z[i][j]])
    next

But I get one list (and not a list of two lists as I want):

[0, 6, -99999, 22, -99999, 22, 15]

How can I get a list of two lists containing the elements after they have been transformed using the dictionary?

CodePudding user response：

You can use nested list comprehension.

t = [[delqType[i] for i in list_i] for list_i in z]
print(t)
[[0, 6, -99999, 22], [-99999, 22, 15]]

CodePudding user response：

You should created the nested lists in t, one for each nested list of z. In addition it will be simpler to iterate the items instead of the indices:

t = []
for sub in z:
    t.append([])
    for item in sub:
        t[-1].append(delqType[item])

Another nice way is to use the itemgetter operator to map the list of keys to the list of values:

from operator import itemgetter
t = [itemgetter(*sub)(delqType) for sub in z]

CodePudding user response：

As you want to get a 2 dimensions list, you need to append a list inside your first for loop.

(But also, please use the for loop to directly extract values, instead of using indices !)

So, this would look like:

t = []
for sublist in z:
    new_sublist = []
    for key in sublist:
        newlist.append(...)
    t.append(new_sublist)

I let to you to fill the internals of the deepest for loop, as an exercise, to ensure you got it correctly :-)

Side note: your code sample is not correct, as there is no next keyword in Python!! Please be sure to provide the exact code you executed.