Merging Linestrings to bigger Linestrings

Question

I have a shapefile with the Linestring elements which looks like this:

Here you see a lot of small lines (about 582 in total). Is there a way to extract pure end-to-end lines? For now, I tried to combine Linestring elements together as the first step by the following code:

def connect_lineparts(geom_list):
    def dfs(adj_list, visited, vertex, result, key):
        visited.add(vertex)
        result[key].append(vertex)
        for neighbor in adj_list[vertex]:
            if neighbor not in visited:
                dfs(adj_list, visited, neighbor, result, key)

    adj_list = defaultdict(list)
    for x, y in geom_list:
        adj_list[x].append(y)
        adj_list[y].append(x)

    result = defaultdict(list)
    visited = set()
    for vertex in adj_list:
        if vertex not in visited:
            dfs(adj_list, visited, vertex, result, vertex)
    return result

When I combine the result points together into Linestring I have something like this:

You can see there are some lines which were created by very distant points and absent of some small lines which were presented initially.

Answer 1

For doing this kind of thing in Python I would recommend looking into the Shapely library, where the linemerge command will combine chains of contiguous LineStrings into larger LineStrings.

If you want to extract 'pure end-to-end lines' you could use the unary_union command to merge all your lines into one MultiLineString, which will then consist of all the (merged) 'pure' lines.