Question

I need to read in a file of sets of coordinates using Python. The first line will have a number, n, which is the number of coordinate sets that need to be read. Following the first line will be n lines, where each line contains a single coordinate pair.

Example (in this case, n =4):

n
(x,y)
(x,y)
(x,y)
(x,y)

The catch is that there will be multiple sections in the file. So the first n might be 10, with 10 sets of coordinates, and the next n might be 20, with 20 sets of coordinates following it.

As of right now I’m just reading the sections of coordinates in separately, but I would like it if I could any number of sections of coordinates in the file I’m reading in.

Answer 1

You can use open() to open a file for reading, readline() to read file content line by line, and int() to convert from a string to an integer.

Here’s an example implementation using these parts:

def read_coords(file_handle):
    try:
        nrecords = int(file_handle.readline())
    except ValueError:
        return False
    return [file_handle.readline() for i in range(nrecords)]

coord_sets = []
with open("some.txt") as f:
   coords = read_coords(f)
   while coords != False:
       coord_sets.append(coords)
       coords = read_coords(f)

print "coord_sets =",coord_sets