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# [mergedeep]
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[PyPi versions]
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[Conda Version]
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[Documentation Status]
A deep merge function for 🐍.
[Check out the mergedeep docs]
## Installation
```bash
$ pip install mergedeep
```
## Usage
```text
merge(destination: MutableMapping, *sources: Mapping, strategy: Strategy =
Strategy.REPLACE) -> MutableMapping
```
Deep merge without mutating the source dicts.
```python3
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.
```python3
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`
```python3
# 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`
```python3
# 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)
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