Using the glom library with Python: Turning a list result into a dictionary with key generated by a Python function

Question

I'm using the Python library glom to extract data from a dictionary that contains lists.

This question is about unterstanding how glom works with user defined functions and how I can move data from lists into dictionaries within glom.

As an example, I'm trying to convert the data into a dictionary directly.

# in the real world, this data has way many more fields
data = {'vessels': [{'aisStatic': {'mmsi': 1, 'name': 'name1'}},
               {'aisStatic': {'mmsi': 2, 'name': 'name2'}}],
       'timestamp': None}

# this is the glob spec to extract the data 
spec = ('vessels',[({'mmsi':'aisStatic.mmsi','name':'aisStatic.name'})])

# an example to generate a new key based on data & position
def keyfunc(i, v):
    return f"v{i}-{v['mmsi']}"

result = glom(data, spec)

wanted_result = {keyfunc(i,v): v for i, v in enumerate(result)}

The wanted result looks like this

{'v0-1': {'mmsi': 1, 'name': 'name1'}, 'v1-2': {'mmsi': 2, 'name': 'name2'}}

For the example, I'm using a comprehension outside of glom to get the wanted result, since glom returns a list.

I am looking at a way to get the same results directly via a glom spec.

576i · Accepted Answer · 2020-02-26T14:53:11.810

A working solution is to use Invoke on the enumerate function.

from glom import merge, Invoke

data = {
    "vessels": [
        {"aisStatic": {"mmsi": 1, "name": "name1"}},
        {"aisStatic": {"mmsi": 2, "name": "name2"}},
    ],
    "timestamp": None,
}

spec = (
    "vessels",
    [{"mmsi": "aisStatic.mmsi", "name": "aisStatic.name"}],
    Invoke(enumerate).specs(T),
    [lambda x: {f"v{x[0]}-{x[1].get('mmsi')}": x[1]}],
    merge,
)

print(glom(data, spec))

which returns the requested result

{'v0-1': {'mmsi': 1, 'name': 'name1'}, 'v1-2': {'mmsi': 2, 'name': 'name2'}}

Using the glom library with Python: Turning a list result into a dictionary with key generated by a Python function

1 Answers1