Extract coordinates from a string using regex in Python

Question

I have multiple strings as below:

LINESTRING (-3.1 2.42, 5.21 6.1, -1.17 -2.23)
LINESTRING (1.83 9.5, 3.33 2.87)

The expected results are lists that contain corresponding coordinates in the tuple format:

[(-3.1,2.42),(5.21,6.1),(-1.17,-2.33)]
[(1.83,9.5),(3.33,2.87)]

Note that the number of coordinates in the string is unknown and variable. Now, I use the split function twice after removing characters outside the parenthesis. Is there any elegant way to exact the coordinates using Regex.

hope this answer helps you: stackoverflow.com/questions/10584339/… — Subbu VidyaSekar
– Subbu VidyaSekar, Commented Aug 31, 2020 at 1:03

Red · Accepted Answer · 2020-08-31 01:27:57Z

2

Here is how you can use a for loop:

import re

strings = ['LINESTRING (-3.1 2.42, 5.21 6.1, -1.17 -2.23)',
           'LINESTRING (1.83 9.5, 3.33 2.87)']

for string in strings:
    st = re.findall('(?<=[(,]).*?(?=[,)])', string)
    print([tuple(s.split()) for s in st])

Output:

[('-3.1', '2.42'), ('5.21', '6.1'), ('-1.17', '-2.23')]
[('1.83', '9.5'), ('3.33', '2.87')]

edited Aug 31, 2020 at 1:27

answered Aug 31, 2020 at 1:07

Red

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Comments

Kirk Strauser · Accepted Answer · 2020-08-31 01:41:20Z

0

Is it a requirement to use regexps? I find plain ol' string splitting to be more maintainable:

strings = [
    "LINESTRING (-3.1 2.42, 5.21 6.1, -1.17 -2.23)",
    "LINESTRING (1.83 9.5, 3.33 2.87)",
]

for s in strings:
    # Collect stuff between parentheses
    inside = s.split("(")[1].split(")")[0]

    pairs = []
    for pair in inside.split(", "):
        left, right = pair.split(" ")
        pairs.append((float(left), float(right)))

    print(pairs)

This isn't a super clever solution -- it's pretty brute force -- but if it breaks at 2AM I think I'd be able to figure out what it's actually doing.

answered Aug 31, 2020 at 1:41

Kirk Strauser

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