Appending new keys and values to a dictionary in a nested for loop without overwriting old entries-CodePudding

I have two data sources (Subjects) which are loaded via np.loadtxt into Python.

The loop for ROI in ROIs is nested in the loop for Subject in Subjects.

My aim is to append the computational results of PLE = sp.stats.linregress(np.log(Ideal_frequency), np.log(Data)) of both subjects for each ROI into the dictionary. The code should append the result of PLE[0] of both subjects together into one list or array for each ROI.

My problem that I am unable to solve is that my code only appends the computational result PLE[0] for Subject1 into PLE_dict. Consequently, Subject2 is not included.

For example, printing the result via PLE_dict yields:

{1: [-0.9924575013746104],
 2: [-0.8905778114042852],
 3: [-1.0143346946069933],
.... # Cut the data here

The numbers 1 to 3 represent the first three ROIs, and the values in the square brackets the result of PLE[0]. Both is correct. However, I would also like to append the results of subject2 into the array or list for each ROI.

Here is my current code:

import numpy as np
import scipy as sp
import itertools as it
from scipy import stats


Ideal_frequency = np.loadtxt("/volumes/... .1D")

ROIs = it.chain(range(1,181), range(1001,1181)) # ROIs 1-180 and 1001-1180


Subjects = ["Subject1", "Subject2"]
      
PLE_dict = {}

for Subject in Subjects:
    for ROI in ROIs:
        
        Data = np.loadtxt(f"/volumes/seagate/{Subject}/G360_{ROI}_{Subject}.1D")
       
        PLE = sp.stats.linregress(np.log(Ideal_frequency), np.log(Data))
        
        if ROI not in PLE_dict:
            PLE_dict[ROI] = [PLE[0]]
        else:
            PLE_dict[ROI].append(PLE[0])

             
            

print(PLE_dict)

This screenshot maybe describes the problem better. Here is the output of print(PLE_dict). It shows the results of PLE[0] for the last ROIs (one ROI per row). But these results are only for subject1. My aim is to add the results of subject2 into the same rows for the single ROIs.

CodePudding user response：

You can solve this by:

        if ROI not in PLE_dict:
            PLE_dict[ROI] = [PLE[0]]
        else:
            PLE_dict[ROI].append(PLE[0])

Running

PLE_dict = {}

for Subject in range(2):
    for ROI in range(2):
        
        if ROI not in PLE_dict:
             PLE_dict[ROI] = [Subject*ROI]
        else:
             PLE_dict[ROI].append(Subject*ROI)

print(PLE_dict)

gives

{0: [0, 0], 1: [0, 1]}

Also

it.chain(range(1,181), range(1001,1181)) # ROIs 1

is an iterator and once iterated, it is empty and will not run a second time. So either turn it into a list of put it directly into the loop.