How can I create an array from a messy text file - python-2.7

Question

I have a text file in the form below...
Some line of text
Some line of text
Some line of text
--
data entry 0 (i = 0, j = 0); value = 1.000000
data entry 1 (i = 0, j = 1); value = 1.000000
data entry 2 (i = 0, j = 2); value = 1.000000
data entry 3 (i = 0, j = 3); value = 1.000000
etc for quite a large number of lines. The total array ends up being 433 rows x 400 columns. There is a line of hyphens -- separating each new i value. So far I have the following code:
f = open('text_file_name', 'r')
lines = f.readlines()
which is simply opening the file and converting it to a list with each line as a separate string. I need to be able create an array with the given values for i and j positions - let's call the array A. The value of A[0,0] should be 1.000000. I don't know how I can get from a messy text file (at the stage I am, messy list) to a usable array
EDIT:
The expected output is a NumPy array. If I can get to that point, I can work through the rest of the tasks in the problem
UPDATE:
Thank you, Lukasz, for the suggestion below. I sort of understand the code you wrote, but I don't understand it well enough to use it. However, you have given me some good ideas on what to do. The data entries begin on line 12 of the text file. Values for i are within the 22nd and 27th character places, values for j are within the 33rd and 39th character places, and values for value are within the 49th and 62nd character places. I realize this is overly specific for this particular text file, but my professor is fine with that.
Now, I've written the following code using the formatting of this text file
for x in range(12,len(lines)):
if not lines[x].startswith(' data entry'):
continue
else:
i = int(lines[x][22:28])
j = int(lines[x][33:39])
r = int(lines[x][49:62])
matrix[i,j] = r
print matrix
and the following ValueError message is given:
r = int(lines[x][49:62])
ValueError: invalid literal for int() with base 10: '1.000000'
Can anyone explain why this is given (I should be able to convert the string '1.000000' to integer 1) and what I can do to correct the issue?

Answer 1

You may simply skip all lines that does not look like data line.
For retrieving indices simple regular expression is introduced.
import numpy as np
import re
def parse(line):
m = re.search('\(i = (\d+), j = (\d+)\); value = (\S+)', line)
if not m:
raise ValueError("Invalid line", line)
return int(m.group(1)), int(m.group(2)), float(m.group(3))
R = 433
C = 400
data_file = 'file.txt'
matrix = np.zeros((R, C))
with open(data_file) as f:
for line in f:
if not line.startswith('data entry'):
continue
i, j, v = parse(line)
matrix[i, j] = v
print matrix
Main trouble here is hardcoded matrix size. Ideally you' somehow detect a size of destination matrix prior to reading data, or use other data structure and rebuild numpy array from said structure.