CODEWITHSUNDEEP
python
Parvez Ahmed
Parvez Ahmed

Reputation: 19

Reading values from a text file with different row and column size in python

I have read other simliar posts but they don't seem to work in my case. Hence, I'm posting it newly here.

I have a text file which has varying row and column sizes. I am interested in the rows of values which have a specific parameter. E.g. in the sample text file below, I want the last two values of each line which has the number '1' in the second position. That is, I want the values '1, 101', '101, 2', '2, 102' and '102, 3' from the lines starting with the values '101 to 104' because they have the number '1' in the second position. 

$MeshFormat
2.2 0 8
$EndMeshFormat
$Nodes
425
.
.
$EndNodes
$Elements
630
.
97 15 2 0 193 97
98 15 2 0 195 98
99 15 2 0 197 99
100 15 2 0 199 100
101 1 2 0 201 1 101
102 1 2 0 201 101 2
103 1 2 0 202 2 102
104 1 2 0 202 102 3
301 2 2 0 303 178 78 250
302 2 2 0 303 250 79 178
303 2 2 0 303 198 98 249
304 2 2 0 303 249 99 198
.
.
.
$EndElements

The problem is, with the code I have come up with mentioned below, it starts from '101' but it reads the values from the other lines upto '304' or more. What am I doing wrong or does someone has a better way to tackle this?

# Here, (additional_lines + anz_knoten_gmsh - 2) are additional lines that need to be skipped 
# at the beginning of the .txt file. Initially I find out where the range 
# of the lines lies which I need.
# The two_noded_elem_start is the first line having the '1' at the second position
# and four_noded_elem_start is the first line number having '2' in the second position. 
# So, basically I'm reading between these two parameters.


input_file = open(os.path.join(gmsh_path, "mesh_outer_region.msh"))
output_file = open(os.path.join(gmsh_path, "mesh_skip_nodes.txt"), "w")

for i, line in enumerate(input_file):                                                
    if i == (additional_lines + anz_knoten_gmsh + two_noded_elem_start - 2):         
        break

for i, line in enumerate(input_file):                                               
    if i == additional_lines + anz_knoten_gmsh + four_noded_elem_start - 2:         
        break

    elem_list = line.strip().split()                
    del elem_list[:5]                               
    writer = csv.writer(output_file)               
    writer.writerow(elem_list)                      

input_file.close()
output_file.close()

*EDIT: The piece of code used to find the parameters like two_noded_elem_start is as follows:

# anz_elemente_ueberg_gmsh is another parameter that is found out 
# from a previous piece of code and '$EndElements' is what 
# is at the end of the text file "mesh_outer_region.msh".

input_file = open(os.path.join(gmsh_path, "mesh_outer_region.msh"), "r")
for i, line in enumerate(input_file):                     
    if line.strip() == anz_elemente_ueberg_gmsh:
        break

for i, line in enumerate(input_file):                    
    if line.strip() == '$EndElements':                    
        break

    element_list = line.strip().split()                   
    if element_list[1] == '1':                            


        two_noded_elem_start = element_list[0]                       
        two_noded_elem_start = int(two_noded_elem_start)            
        break
input_file.close()

Upvotes: 0

Views: 1059

Answers (1)

Chris Seymour
Chris Seymour

Reputation: 85765

>>> with open('filename') as fh:             # Open the file
...    for line in fh:                       # For each line the file
...        values = line.split()             # Split the values into a list
...        if values[1] == '1':              # Compare the second value
...            print values[-2], values[-1]  # Print the 2nd from last and last
1 101
101 2
2 102
102 3

Upvotes: 1

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