Question

I have the following code so far:

import sys
from Tkinter import *
import tkFileDialog
from tkFileDialog import askopenfile # Open dialog box


fen1 = Tk()                              # Create window
fen1.title("Optimisation")               # Window title

menu1 = Menu(fen1)

def open():
    filename = askopenfile(filetypes=[("Text files","*.txt")], mode='r')

filename.seek(0)
    numligne = 0
    line     = []
    ok       = 0
    k        = -1

    while (ok == 0)  &  (k == -1):
    line = filename.readline()
    k    = line.find( "*load" )
    if k == 0 :
        l = filename.readlines()

fen1.mainloop()

The text file I am searching is in the format similar to below:

*test
1 2 3 4

*load
2 7 200
3 7 150

*stiffness
2 9 8 7

etc..

I’ve so far managed to find the line beginning with “*load” but I wish to assign the values in between ‘*load’ and ‘*stiffness’ to variables such as a, b, c. My problem is that in this load section, there could be several lines and I need to detect each one every time, split the values in the lines and give them a name. If someone could please help explain a loop or something similar that would do just the trick, I would be very grateful! Thank you!

UPDATE: I have the problem where I now want to find SEVERAL seperate sections in the same text file. How am I able to create a loop to further find lines between ‘*geo’ and ‘*house’, and also ‘*name’ and ‘*surname’? I’ve tried to create an entirely separate definition but would like to minimize the lines of code I use…Thank you! Code I’ve been using the similar structure for (as provided for my original question, thanks to mgilson!) and would therefore like to edit these type of code.

def parse_file(ff):     
    out=[]     
    append=False     
    for line in ff:         
        if(append and line.strip()):
            out.append(line)          
            if(line.startswith('*load')): 
                append=True
            elif(line.startswith('*stiffness')):  
                return [map(int,x.split()) for x in out[:-1] ] 

Answer 1

Let’s assume that your “blocks” of code are separated by headers (e.g. *header). The most intuitive way to store the data in each block is in a list of lists. e.g. [ row1, row2, ...] (where row1=[elem1,elem2,elem3,...]). Then you can store the block in a dictionary so you can get access to the block via block=dictionary['headername'].

This will do something like what you want (this version is untested).

import sys

def convert_type(ss):
    try:
        return int(ss)
    except ValueError:
        try:
            return float(ss)
        except ValueError:
            return ss

def parse_file(ff):
    out={}
    block=None
    for i,line in enumerate(ff):
        #Allow for comments to start with '#'.  We break off anything after a '#'
        #and ignore it.  After that, we 
        data=line.split('#',1)
        line=data[0]  #comments (if in line) are in data[1] ... ignore those.
        line=line.strip() #remove whitespace from front and back of line.
        if(line.startswith('*')):
            #python supports multiple assignment.  
            #e.g. out['header'] is the same object as block.  
            #     changing block also changes out['header']
            block=out[line.strip()[1:]]=[]
        elif (block is not None) and line: #checks to make sure there is an active block and the line wasn't empty.
            #If the file could also have floats, you should use float instead of int
            #We also put the parsing in a try/except block.  If parsing fails (e.g. a
            #element can't be converted to a float, you'll know it and you'll know the
            #line which caused the problem.)
            try:
                #block.append(map(int,line.split()))
                block.append(map(convert_type,line.split()))  
            except Exception:
                sys.stderr.write("Parsing datafile choked on line %d '%s'\n"%(i+1,line.rstrip()))
                raise
    return out

with open('textfile.txt','r') as f:
    data_dict=parse_file(f)

#get information from '*load' block:
info=data_dict['load']
for row in info:
    a,b,c=row
    ##same as:
    #a=row[0]
    #b=row[1]
    #c=row[2]
    ##as long as row only has 3 elements.

    #Do something with that particular row. 
    #(each row in the 'load' block will be visited once in this loop)

#get info from stiffness block:
info=data_dict['stiffness']
for row in info:
    pass #Do something with this particular row.

Note that if you’re guaranteed that each row in the datafile under a certain header has the same number of entries, you can think of the variable info as a 2-dimensional row which is indexed as element=info[row_number][column_number] — but you can also get an entire row by row=info[row_number]