mergedeep

A deep merge function for 🐍.

Check out the mergedeep docs

Installation

$ pip install mergedeep

Usage

merge(destination: MutableMapping, *sources: Mapping, strategy: Strategy = Strategy.REPLACE) -> Mapping

Deep merge without mutating the source dicts.

from mergedeep import merge

a = {"keyA": 1}
b = {"keyB": {"sub1": 10}}
c = {"keyB": {"sub2": 20}}

merged = merge({}, a, b, c) 

print(merged)
# {"keyA": 1, "keyB": {"sub1": 10, "sub2": 20}}

Deep merge into an existing dict.

from mergedeep import merge

a = {"keyA": 1}
b = {"keyB": {"sub1": 10}}
c = {"keyB": {"sub2": 20}}

merge(a, b, c) 

print(a)
# {"keyA": 1, "keyB": {"sub1": 10, "sub2": 20}}

Merge strategies:

1. Replace (default)

Strategy.REPLACE

# When `destination` and `source` keys are the same, replace the `destination` value with one from `source` (default).

# Note: with multiple sources, the `last` (i.e. rightmost) source value will be what appears in the merged result. 

from mergedeep import merge, Strategy

dst = {"key": [1, 2]}
src = {"key": [3, 4]}

merge(dst, src, strategy=Strategy.REPLACE) 
# same as: merge(dst, src)

print(dst)
# {"key": [3, 4]}

2. Additive

Strategy.ADDITIVE

# When `destination` and `source` values are both the same additive collection type, extend `destination` by adding values from `source`.
# Additive collection types include: `list`, `tuple`, `set`, and `Counter`

# Note: if the values are not additive collections of the same type, then fallback to a `REPLACE` merge.

from mergedeep import merge, Strategy

dst = {"key": [1, 2], "count": Counter({"a": 1, "b": 1})}
src = {"key": [3, 4], "count": Counter({"a": 1, "c": 1})}

merge(dst, src, strategy=Strategy.ADDITIVE) 

print(dst)
# {"key": [1, 2, 3, 4], "count": Counter({"a": 2, "b": 1, "c": 1})}

3. Typesafe replace

Strategy.TYPESAFE_REPLACE or Strategy.TYPESAFE

# When `destination` and `source` values are of different types, raise `TypeError`. Otherwise, perform a `REPLACE` merge.

from mergedeep import merge, Strategy

dst = {"key": [1, 2]}
src = {"key": {3, 4}}

merge(dst, src, strategy=Strategy.TYPESAFE_REPLACE) # same as: `Strategy.TYPESAFE`  
# TypeError: destination type: <class 'list'> differs from source type: <class 'set'> for key: "key"

4. Typesafe additive

Strategy.TYPESAFE_ADDITIVE

# When `destination` and `source` values are of different types, raise `TypeError`. Otherwise, perform a `ADDITIVE` merge.

from mergedeep import merge, Strategy

dst = {"key": [1, 2]}
src = {"key": {3, 4}}

merge(dst, src, strategy=Strategy.TYPESAFE_ADDITIVE) 
# TypeError: destination type: <class 'list'> differs from source type: <class 'set'> for key: "key"

License

MIT © Travis Clarke