“Coordinates” are a way to locate a nested item in a data.

Consider the following data—a list of persons:

data = [
        'name': 'Alice',
        'age': 30,
                'name': 'Carl',
                'age': 8

        'name': 'Bob',
        'age': '40',
        'children': []

To access the age of the first person (i.e. Alice) in the list, you do this:

data[0]['age'] # data > first item > age

Coordinates is basically a string containing the chain of the keys and indices to locate a field in the data.


To join the coordinates into a string, we use a special symbol called the section sign (§). Earlier, we used the hyphen (-) as the separator, but that made it impossible for the schema object keys (i.e. field names) to contain the hyphen.

So, for above example, the coordinates string is: '0§age'. We’ve just chained the index and key into a string.

To access the age of the first child (i.e. Carl) of first person (i.e. Alice) in the list, you perform this lookup:

data[0]['children'][0]['age'] # data > first item > children > first item > age

This time, the coordinates string is: '0§children§0§age'.

To make it easier to generate the coordinates string and to avoid copying and pasting the section symbol, you can use the join_coords() helper function:

from django_jsonform.utils import join_coords

join_coords(0, 'age') # -> '0§age'

Uses of coordinates

1. Displaying error messages

Coordinates are used by the library for displaying error messages for a field.

To display error message under the age field of first person, you can do this:

error_map = {
    '0§age': 'Invalid value',

The library will use the coordinates to display an error message under the appropriate field.

Alternatively, instead of manually copying this symbol, you can use the ErrorMap helper class to create the error map.

2. In handler views

You can use the coordinates in a file handler view or autocomplete handler view to determine the field in the schema which sent the request.

This is useful if you have one common handler for multiple schemas and you want to return different response based on the schema field.

To split coordinates string into individual coordinates, use the split_coords() helper function:

from django_jsonform.utils import split_coords

split_coords('0§age') # -> ['0', 'age']