8.17. Builtin Reduce

• Reduce sequence using function

• Built-in

>>> 1 + 2
3

>>> 1 + 2 + 3 + 4
10

8.17.1. Syntax

• functools.reduce(function, iterable[, initializer])

• required callable - Function

• required iterable - Sequence or iterator object

• https://docs.python.org/library/functools.html

8.17.2. Problem

>>> def add(x, y):
...     return x + y
>>>
>>>
>>> DATA = [1, 2, 3, 4]
>>> result = 0
>>>
>>> for element in DATA:
...     result = add(result, element)
>>>
>>> print(result)
10

8.17.3. Solution

>>> from functools import reduce
>>>
>>>
>>> def add(x, y):
...     return x + y
>>>
>>>
>>> DATA = [1, 2, 3, 4]
>>>
>>> reduce(add, DATA)
10

8.17.4. Rationale

• https://docs.python.org/library/operator.html

>>> from functools import reduce
>>> from operator import mul
>>>
>>>
>>> DATA = [1, 2, 3, 4]
>>>
>>> reduce(mul, DATA)
24

>>> from functools import reduce
>>>
>>>
>>> DATA = [1, 2, 3, 4]
>>>
>>> reduce(min, DATA)
1
>>> reduce(max, DATA)
4

8.17.5. Map Reduce

• https://dask.org