Matching two lists values and appending to dictionary - python-3.x

Question

I have a list of nodes with their coordinates of the form
MCoord = [[Node1,X,Y,Z],[Node2,X,Y,Z]...]
Coordinates:
MCoord = [
[1, 0, 0, 0],
[2, 0, 1000, 1300],
[3, 0, 2000, 2000],
[4, 0, 3000, 2500],
[5, 0, 4000, 3200],
[6, 0, 5000, 4200],
[7, 0, 6000, 6000],
[8, 1000, 0, 0],
[9, 1000, 1000, 1300],
[10, 1000, 2000, 2000],
[11, 1000, 3000, 2500],
[12, 1000, 4000, 3200],
[13, 1000, 5000, 4200],
[14, 1000, 6000, 6000],
[15, 2000, 0, 0],
[16, 2000, 1000, 1300],
// ...
[27, 3500, 5000, 4200],
[28, 3500, 6000, 6000]
]
I want to store all nodes (with their coordinates) of the same X coordinate and matching the corresponding key value under the keys S1 (all nodes with same X value), S2, S3 and so on.
Script:
SectionLocation = {'S1':0 , 'S2':1000 , 'S3':2000 , 'S4':3500}
SectionComplete = {'S1':0 , 'S2':0 , 'S3':0 , 'S4':0}
k = 0
for i in range(len(MCoord)):
print(i)
if MCoord[i][1] == SectionLocation[k]:
keydic = get_key(SectionLocation[k])
SectionComplete[keydic].append(MCoord[i])
print(SectionComplete)
else:
k = k + 1
print(SectionComplete)
I cannot seem to be able to append new values to the dictionnary. Any advice ?
Desired outpput:
SectionComplete = {
'S1' : [
[1, 0, 0, 0],
[2, 0, 1000, 1300],
[3, 0, 2000, 2000],
[4, 0, 3000, 2500],
[5, 0, 4000, 3200],
[6, 0, 5000, 4200],
[7, 0, 6000, 6000]
],
'S2' : [
[8, 1000, 0, 0],
[9, 1000, 1000, 1300],
[10, 1000, 2000, 2000],
[11, 1000, 3000, 2500],
[12, 1000, 4000, 3200],
[13, 1000, 5000, 4200],
[14, 1000, 6000, 6000]
],
// ...
}

Answer 1

I believe this is what you are attempting to achieve. But you can correct me if I'm wrong.
# your list of nodes and coordinates
MCoord = [[1, 0, 0, 0],
[2, 0, 1000, 1300],
[3, 0, 2000, 2000],
[4, 0, 3000, 2500],
[5, 0, 4000, 3200],
[6, 0, 5000, 4200],
[7, 0, 6000, 6000],
[8, 1000, 0, 0],
[9, 1000, 1000, 1300],
[10, 1000, 2000, 2000],
[11, 1000, 3000, 2500],
[12, 1000, 4000, 3200],
[13, 1000, 5000, 4200],
[14, 1000, 6000, 6000],
[15, 2000, 0, 0],
[16, 2000, 1000, 1300]]
# a dictionary mapping of section to its ID
SectionLocation = {0: 'S1', 1000: 'S2', 2000: 'S3', 3500: 'S4'}
# A dictionary of the grouped sections
SectionComplete = {'S1': [], 'S2': [], 'S3': [], 'S4': []}
# we don't need the index since python for loops take care of that for us
for node in MCoord:
# grab the relevant section from the mapping
section = SectionLocation[node[1]]
# append it to that sections empty list
SectionComplete[section].append(node)
print(SectionComplete)
In your example here SectionComplete = {'S1':0 , 'S2':0 , 'S3':0 , 'S4':0} you initialize your dict values to ints and then are trying to append to those ints. Essentially it's like trying to do something like this.
my_int = 0
my_int.append(23)
This won't work because an int does not have an append method.

Answer 2

MCoord = [[...]]
import numpy as np
array_of_coords = np.array((MCoord))
uniq_X = np.unique(array_of_coords[:,1])
group_by_X = [[array_of_coords[array_of_coords[:,1]==i,:] for i in uniq_X]]
list_of_keys = ["S"+str(i) for i in range(len(uniq_X))]
dictionary = dict(zip(list_of_keys, group_by_X[0]))
print(dictionary)
out:
{'S0': array([[ 1, 0, 0, 0],
[ 2, 0, 1000, 1300],
[ 3, 0, 2000, 2000],
[ 4, 0, 3000, 2500],
[ 5, 0, 4000, 3200],
[ 6, 0, 5000, 4200],
[ 7, 0, 6000, 6000]]), 'S1': array([[ 8, 1000, 0, 0],
[ 9, 1000, 1000, 1300],
[ 10, 1000, 2000, 2000],
[ 11, 1000, 3000, 2500],
[ 12, 1000, 4000, 3200],
[ 13, 1000, 5000, 4200],
[ 14, 1000, 6000, 6000]]), 'S2': array([[ 15, 2000, 0, 0],
[ 16, 2000, 1000, 1300]])}