I have n lists as below:

List_1 = ['x1', 'y1', 'z1']

List_2 = ['x2', 'y2', 'z2']

List_3 = ['x3', 'y3', 'z3']
...
List_n = ['xn', 'yn', 'zn']

list_dict = {List_1: 'yes', List_2: 'yes', List_3: 'no', ..., List_n: 'yes'}

I want to make one larger list comprising of subset of smaller n lists and criteria to append members of a smaller list is defined in this dictionary 'list_dict', i.e. append members of List_1, List_2, List_n BUT NOT List_3

Final_List = ['x1', 'y1', 'z1', 'x2', 'y2', 'z2', ...., 'xn', 'yn', 'zn']

Also, it is preferable to use list comprehension OR lambda function to generate Final_List but not a must.

NOTE: 'list_dict' i.e. the criteria to append any smaller list does not have to be a dictionary if alternative options are available. NOW I cant define 'list_dict' using keys are variable names defined outside of 'list_dict', so maybe replacing variable name with equivalent strings is one option to define the dictionary such as below:

list_dict = {'List_1': 'yes', 'List_2': 'yes', 'List_3': 'no', ..., 'List_n': 'yes'}

BUT THEN we need a way to dynamically access strings as variable name using globals() method in namespace.

CodePudding user response：

The simplest thing is to keep a list of your lists, and do something like:

big_list = [['x1', 'y1', 'z1'], ['x2', 'y2', 'z2'], ['x3', 'y3', 'z3'], ['x4', 'y4', 'z4']]
list_dict = {1:True, 2:True, 3:False, 4:True}

Then you can easily build your final list:

final_list = [item for i, sub_list in enumerate(big_list, start=1) if list_dict[i] for item in sub_list]
final_list #['x1', 'y1', 'z1', 'x2', 'y2', 'z2', 'x4', 'y4', 'z4']

CodePudding user response：

Here's a way to do what your question asks without needing a dict, and hence avoiding the issue of hashing lists as "keys" in a dictionary:

List_1 = ['x1', 'y1', 'z1']

List_2 = ['x2', 'y2', 'z2']

List_3 = ['x3', 'y3', 'z3']

List_n = ['xn', 'yn', 'zn']

#list_dict = {List_1: 'yes', List_2: 'yes', List_3: 'no', List_n: 'yes'}
list_mask = [(List_1, 'yes'), (List_2, 'yes'), (List_3, 'no'), (List_n, 'yes')]


from functools import reduce
from operator import add
Final_List = reduce(add, (lst for lst, yesNo in list_mask if yesNo == 'yes'))
print(Final_List)

Output:

['x1', 'y1', 'z1', 'x2', 'y2', 'z2', 'xn', 'yn', 'zn']

Explanation:

• replace list_dict with list_mask, a list of pairs (I have used tuples, but lists would be fine as well) each containing a list reference and a yes/no string
• use a generator comprehension to create an iterable of the lists marked yes
• use the reduce function from functools together with add from operator to concatenate all these lists.

Note: If there's a possibility of duplicate members across different input lists, and we want the output list to have no duplicates, we can do this:

from functools import reduce
from operator import add
list_maybe_nonunique = reduce(add, (lst for lst, yesNo in list_mask if yesNo == 'yes'))
found = set()
Final_List = []
for item in list_maybe_nonunique:
    if item not in found:
        found.add(item)
        Final_List.append(item)
print(Final_List)