[Python] How to implement custom indentation when pretty-printing with the JSON module?

So I'm using Python 2.7, using the json module to encode the following data structure:

'layer1': {
'layer2': {
'layer3_1': [ long_list_of_stuff ],
'layer3_2': 'string'
}
}


My problem is that I'm printing everything out using pretty printing, as follows:

json.dumps(data_structure, indent=2)


Which is great, except I want to indent it all, except for the content in "layer3_1" — It's a massive dictionary listing coordinates, and as such, having a single value set on each one makes pretty printing create a file with thousands of lines, with an example as follows:

{
"layer1": {
"layer2": {
"layer3_1": [
{
"x": 1,
"y": 7
},
{
"x": 0,
"y": 4
},
{
"x": 5,
"y": 3
},
{
"x": 6,
"y": 9
}
],
"layer3_2": "string"
}
}
}


What I really want is something similar to the following:

{
"layer1": {
"layer2": {
"layer3_1": [{"x":1,"y":7},{"x":0,"y":4},{"x":5,"y":3},{"x":6,"y":9}],
"layer3_2": "string"
}
}
}


I hear it's possible to extend the json module: Is it possible to set it to only turn off indenting when inside the "layer3_1" object? If so, would somebody please tell me how?

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