Updating Z value within XYZ.txt file using ArcPy?

Question

Following Creating polygon from 2 txt files (Parent ID + Coordinates) from a few weeks ago, the script works very well. Now I need to reverse the process in order to update the Z value in the original text file describing a mesh.

From a first table of Points coordinates (Nnodes, resulting from Export Feature Attribute to ASCII):

 #Nnodes
 # X Y ID Z
 4403607.48  5788195.96  56362  87.6
 4403550.41  5788192.5  56951  93.4

I want to update the Z value from Nnodes to Mesh_orig,using the Point IDs as common keys

 # Mesh_orig
 #Geom ID X Y Z
 ND 56362 4403607.48 5788195.96 86.1
 ND 56951 4403550.41 5788192.5 91.3

It prints only the last row of Nnodes instead of the whole updated mesh_dict.

 with open (r'text2.txt','r+') as Mesh: 
      for row in Mesh:
          if row.startswith('ND'): 
              Inline= row.split()
              mesh_dict={Inline[1]:Inline[4]}
              KeyM = mesh_dict.keys()
              ValueM = mesh_dict.values()    

 with open (r'Text1.txt','r') as Npoint:
     for KeyM in mesh_dict:
         for lines in Npoint:
             Outlines= lines.split()
             point_dict={Outlines[-2]:Outlines[-1]}
             KeyP = point_dict.keys()
             ValueP = point_dict.values()
             if KeyM in point_dict:
                    point_dict.update(mesh_dict) 
                    print str(KeyM)+", "+str(ValueP)

Where is it going wrong?

Answer 1

When you're trying to assign the key to mesh_dict in the first loop you're actually overwriting it with a new dictionary on every iteration of the loop. Instead you should define the dictionary outside the loop and then set the dictionary values like so:

mesh_dict {}
for row in Mesh:
    if row.startswith('ND'):
        Inline= row.split()
        mesh_dict[Inline[1]] = Inline[4]

Answer 2

Here is the working code updating one of two dictionaries based on common keys:

Mesh_dict={}
Point_dict={}
Mesh = open (r'short3.txt','r+')  
for row in Mesh:
   # extract lines describing one type of geometry
    if row.startswith('ND'): 
    Inline= row.split()
    IDM = Inline[1]
    ZM = Inline[4]
    # actualise the dictionary of original data
    Mesh_dict[IDM]=ZM

Npoint= open (r'new_pt.txt','r')
for lines in Npoint:
    Outlines= lines.split()                
    IDP = Outlines [-2]
    ZP = Outlines[-1]
    Point_dict [IDP]=ZP      
for k1,v1 in Mesh_dict.items():
    for k2,v2 in Point_dict.items():
        if k1 ==k2:
           Mesh_dict[k1] = v2