A multi level nested list

Question

I am trying to implement a customized automata where the transition table looks like:

The table is dynamic i.e. the column heading, row name, and data at every cell can be determined at run time. The column name and row name are also necessary.

I tried this code

table = []
table.append(["A",[0,["B",2],["C1",2]],[1,["C1",1]]])
table.append(["B",[0,["C",1]],[1,["C2",1]]])
table.append(["C",[0,["C1",1]],[1,["C2",1]]])

but I am unable to access the individual item in the cell i.e. B or 2 from B:2 etc. Then I tried

row = ["A","B","C","C1","C2"]
col = [0,1]
table = [] 
table.append([[["B",2],["C1",2]],["C1",1]])
table.append([["C",1],["C2",1]])
table.append([["C1",1],["C2",1]])

print(table[0][0][0][0])

Now, I can access the individual item (B in the above case) but I am lost with the four subscript. Specially, when I do not know the depth of the list in advance. Need to get some help to do it in some easy way. Being a novice, I will appreciate some explanation to the pythonic code.

Update: This is Non-deterministic Finite Automata. I tried the automaton package but they are not solving my problem. Following the solution of Tadhg-Mcdonald-Jensen, it give the correct out put for the first row (A) in the table but an error message for second row (B). Here is the code

table = {}
table["A"] = {0: {"B":2, "C1":2}, 1: {"C1":1}}
table["B"] = {0: {"C":1},         1: {"C2",1}}
table["C"] = {0: {"C1":1},        1: {"C2",1}}

for key,value in table["A"][0].items():  \\ok treated as dictionary (1)
    print(key, value, sep="\t")        
for key,value in table["A"][1].items():  \\ok treated as dictionary (2)
    print(key, value, sep="\t")          
for key,value in table["B"][0].items():  \\ok treated as dictionary (3)
    print(key, value, sep="\t")          
for key,value in table["B"][1].items():  \\wrong: why treated as set? Although same as (2)
    print(key, value, sep="\t")          \\Error message: AttributeError: 'set' object has no attribute 'items'

The output is

B   2
C1  2 
C1  1
C   1
Traceback (most recent call last):
  File "C:/Users/Abrar/Google Drive/Tourism Project/Python Projects/nestedLists.py", line 17, in <module>
for key,value in table["B"][1].items():
AttributeError: 'set' object has no attribute 'items'

I would suggest you to look into pandas (http://pandas.pydata.org/). It's built for specifically handling tabular data and you will be able to access elements very easily using index and column names. — Ankur Ankan, Oct 24 '17 at 21:48
I tried but having same confusion of accessing the multilevel nested elements. I am giving it another try. Thanks — Dr. Abrar, Oct 24 '17 at 21:57
PANDAS is perfectly happy to handle nested lists within a table. You just have to make sure you feed it the proper diet of punctuation. — Prune, Oct 24 '17 at 22:07
The errors you show at the end of your code have to do with these entries: `{"C2",1}`. You want `{"C2": 1}` (with a colon instead of a comma). — Blckknght, Oct 25 '17 at 06:29

Tadhg McDonald-Jensen · Accepted Answer · 2017-10-28T18:18:50.763

2

Pandas is great at doing tables but you could also move to dictionaries, either way, list is not the data structure you want.

table = {}
table["A"] = {0: {"B":2, "C1":2}, 1: {"C1":1}}
table["B"] = {0: {"C":1},         1: {"C2":1}}
table["C"] = {0: {"C1":1},        1: {"C2":1}}

Then table["A"][0] will give you the first element, each element will have one or more entries, if you wanted to iterate over the entries you can do for key,value in table["A"][0].items()

Or to iterate over the entire table you could use 3 nested for loops:

#do_stuff = print
for row, line in table.items():
    #each row in the table, row will go through ("A", "B", "C")
    for column, cell in line.items():
        #each cell in the row, column will go through (0, 1)
        for label, value in cell.items(): 
            #each entry in cell, most only have one entry except table["A"][0]
            do_stuff(row, column, label, value)

To be honest I don't understand what the table represents so I can't give you specific advice but I think this would at least be a clearer data structure.

edited Oct 28 '17 at 18:18

answered Oct 25 '17 at 00:28

Tadhg McDonald-Jensen

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You have a typo on both of the `C2` entries. You need colons instead of commas: `{"C2": 1}`. With a comma you get a set instead of a dictionary. – Blckknght Oct 25 '17 at 06:30
Thank you so much Blcknght. I am novice. – Dr. Abrar Oct 25 '17 at 06:34
@Abrar next time an answer gives you issues please comment on the answer, that way I'd get a notification that you asked a clarifying question and can respond with help. :) – Tadhg McDonald-Jensen Oct 28 '17 at 16:26
@TadhgMcDonald-Jensen Thank you so much for updated answer. You saved my days by giving the iterative solution. Can you tell me that how can I update the table if I want want to find and key in the table and increment its associated values. Like for B, i need to increment :2 to 3 and if the key in not present in the table I will add {'New':1} to corresponding key. Is it okay to ask it here or I need to ask another question? Thanks for your guidance. – Dr. Abrar Oct 29 '17 at 22:19
@Abrar to add entries to a cell look at [this question](https://stackoverflow.com/questions/473099/check-if-a-given-key-already-exists-in-a-dictionary-and-increment-it). And know that [`Counter`](https://docs.python.org/3/library/collections.html#collections.Counter) works like `defaultdict(int)`. So you'd have something like `table['A'] = {0:Counter(B=2, C1=2), 1:Counter(C1=1)}`. If that question doesn't solve your issue then you would post a new question. :) – Tadhg McDonald-Jensen Nov 01 '17 at 12:17
@TadhgMcDonald-Jensen Thank you so much.The issue is resolved :) – Dr. Abrar Nov 02 '17 at 04:40

A multi level nested list

1 Answers1