I have a dictionary with lots of data from a CSV file where the key is the row number and the value is a list that contains the column data.

What I want to do is to check from a data of each line (key) and from column 2, I take its data from column 4 and then look for this data in column 2 of another line (key) and take its data in column 4 and continue until it finds the last value of column 4 in column 2.

My code is this:

dict_FH_coord = self.dict_FH() 
site_SI='some_site'       
list_test = [site_SI]

while len(list_test) > 0:
    for ele in list_test:
        for cle, val in dict_FH_coord.items():
            list_test = []
            if val[2] == ele:
                list_test.append(val[4])
                list_def.append(val)
                print(val)

But this code does not work because it stops at the first iteration and it finds that the elements linked to the starting site_SI only

Is there a way to do successive iterations with the list list_test which becomes dynamic to solve my problem?

CodePudding user response：

Can you provide an example of what you are trying to achieve?

CodePudding user response：

If you want to modify list 'on air' you sohuld do something like

a = [1, 2, 3]
a[:] = [1, 2]

In your case the only way you may use this inside the loop (avoiding infinite list size increasement):

if val[2] == ele:
    list_test[:] = list_test[1:] [val[4]]
    list_def.append(val)
else:
    list_test[:] = list_test[1:]

But it wont work as intended because previous iteration ends at index 1 (for ele in list_test:), and list_test would never change in size.

Both this cases can not be merged with each other.

I suggest you to use Queue, but be careful to avoid infinite links looping inside your data:

from queue import Queue
dict_FH_coord = {
    1: [0, 1, 'some_site', 3, 'some_site_2'],
    2: [0, 1, 'some_site_2', 3, 'some_site_3'],
    3: [0, 1, 'some_site_2', 3, 'some_site_4'],
    4: [0, 1, 'some_site_3', 3, 'some_site_5'],
}
site_SI = 'some_site'
unvisited = Queue()
unvisited.put(site_SI)
list_def = list()
while not unvisited.empty():
    ele = unvisited.get()
    for cle, val in dict_FH_coord.items():
        if val[2] == ele:
            unvisited.put(val[4])
            list_def.append(val)
            print(val)